If you look at the most popular shonen series, you'll notice that the main characters practically always have the most basic and boring powers compared to their side characters and villains. It's always variations on super strength, super speed, durability, flight, and maybe an energy blast if we're generous. Nearly all their power comes from stat increases, not from an actual supernatural ability.

When this is criticized, many people claim that it's simply unrealistic to expect any sort of exciting powersets from the protagonist. However, I think that's a copout response. I think there's pretty much no reason why a protagonist should not have a complex powerset.

Note that this applies to pretty much all series involving supernatural abilities. Comic books and western media are slightly better about it on average in terms of giving protagonists interesting powers, but it's not by much.

Argument 1: We can't make the protagonist insanely OP. They'd instantly win every single battle.

Just because a powerset is more complex doesn't mean it's more overpowered. In fact, having a more complex power with conditions can make it less overpowered because it has activation requirements before it can be used.

We're not asking for the protagonists to immediately become universal reality warpers. The breadth of their power can still be scaled to the appropriate level for the series. Just because we're giving a protagonist the ability to transmute water into wood doesn't mean that we want them to be solidifying oceans at a time.

Plus most of the time shonen protagonists are already continent busting or whatever. Even with just their raw stats, the protagonists are power scaled to insanely high levels in the middle of the series. Is it really a huge buff if they're granted poison manipulation instead of punching away continents?

Argument 2: Giving the protagonist an interesting ability would take too long to explain, and the viewers are too stupid to understand complex powers.

This argument falls flat since most of the time, villains and side characters all have incredibly complex powers which need to be explained. Those powers are explained frequently while the protagonist's complex power only needs to be explained once.

Argument 3: There's no way to give the protagonist an interesting ability and have them participate in multiple fights. Minor villains can have complex powers since they only show up for one fight.

That's simply not true. There's no difference in power level between a complex powerset and a simple one. Simply by designing fights better and choosing interesting matchups between complex powersets for both sides of the battle, fights can be more strategic and way more interesting than when both sides just have boring super strength and super speed. By having complex powers, the fights have to have actual strategy instead of just "punch harder punch more".

If you're really concerned that the protagonist will be totally unable to contribute in some fights because their power to force objects and people to re-experience events that occurred in their near past by covering them in pollen that they can spit out of their mouth is too situational, just give them multiple powers, something that's also way too rare for shonen protagonists. They can have some boring (but still not too boring) somewhat reliable power like the ability to control paper, and then also they have the power to force events from the past into the present by spitting pollen.

To give you an idea of what I mean by complex powers, I have provided examples of some appropriate powers.

The ability to force objects and people to reundergo events in the near past by spitting pollen on them. This pollen is flammable. The user can search through the past of the object or person that the pollen is on, and select what events to force them to relive. For example, if someone was just healed from an injury, the user could force that injury to temporarily reappear on them. Or by applying the pollen to the eyes and head, the user could force the target to see certain events as they were in the past, not the present. The user can search back further and easier as more pollen is applied.

The ability to shoot psychic beams that attack enemies by replacing their most positive memories with the user's most traumatic memories.

The ability to produce energy-conducting wires out of the water in their body. The user pulls metal wires from the water in their body, so use of the power dehydrates them. The user attunes the wire to conduct a particular energy, whether that be light, forces, shockwaves, heat, electricity, or microwaves. Then, the user can transport energy of that form that touches the wire at a certain point up and down the wire and release it elsewhere. The wires only have special energy conducting properties within a radius around the user. Once they're moved far away from the user, they just become regular metal wires. An arbitrarily large amount of energy can be transported through these wires, but it must be transferred. It cannot be stored.

The ability to create a projection that can travel kilometers away from you. The projection can peel objects and people slowly like an apple by touching them, damaging them. This peeling ignores durability.

The ability to shift elements into another element up and down the periodic table by touching the compound. The user can selectively up and down shift certain elements. To protect them from their own power, the user can also slow down chemical reactions of their choosing in a short radius around them.

The ability to use the kinetic energy of fast-moving objects in the user's vicinity to speed up the user. This power makes the user faster the more fast-moving things are around them.

The ability to force splice consequences from a variety of possible events in the near future together. In the next 20 seconds, the user can see the possible consequences of multiple decisions that they could make. Then, they can select events that occur out of the variety of timelines and force those consequences to all happen, selectively choosing the good and bad ones.

The ability to create blankets that prevent anyone outside from being able to tell what the blanket is covering as long as there is a piece of glass being covered up by the blanket. If they use x-ray vision or precognition or something to guess what it is covering, the blanket is blown away, uncovering what is underneath it, turns the glass into a portal to a supermassive black hole, and teleports the glass black hole to chase after whoever is looking at it. Additionally, the user can uncover the blanket on their own, automatically turning any piece of glass underneath the blanket into a portal to a black hole.

The ability to create an aura of inefficiency that forces processes to take less efficient paths. The user can force electronics to run slower by making them use algorithms with greater time complexity, becoming more noticeable with larger inputs. The aura can also make biological processes overheat through inefficiency the longer they stay within the field.

The ability to cause the air in a short radius around you to selectively interact with objects. Greater interaction can force fast-moving projectiles to grid to a halt by air resistance. Less interaction can suffocate people, burst their eardrums, and boil their blood as the apparent air pressure drops to 0.

Complex Powers that come from actual series:

Risotto Nero's ability (Jojo's Bizarre Adventure): Metallica allows Nero to manifest blades inside someone by using the iron from their blood. This also prevents them from getting oxygen since they have no iron in them anymore. He can also use the power to manifest blades out of his own blood to sew back on damaged body parts. It also gives him regular magnetic powers, allowing him to move metal and attract it to himself. Metallica also allows Nero to turn invisible.

Kashii Rin's ability (Battle Game in 5 Seconds): Iron Maiden allows Rin to turn her bodily fluids into any instrument of torture. This includes red-hot pokers, spikes, iron maiden jails, and handcuffs. She usually fights by flinging sweat droplets at her enemy, which she turns into spikes midair.

Giorno Giovanna's ability (JJBA): Notable as he is an actual protagonist. Giorno's power allows him to transform non-living things into living things. He can turn objects into plants and animals. Those non-living things then have damage reflection properties. He can also inject people with life-force causing their senses to accelerate compared to their actual body. He learns to heal people by transforming objects into flesh he can repair people with.

Rain (Worm): Rain has the ability to throw boomerangs that create lines of fragility that cause the target to break easily across those lines. This ignores durability He can also cancel his momentum to give him better balance. He can also quickly craft prosthetic limbs. Finally, he has the power to inflict guilt and doubt over an area.

Orihime (Bleach): Orihime's tragically underused power allows her to reject the reality of events within her shield. Her triangular shield can serve as a normal forcefield, but can also heal people within by rejecting their wounds. She can also shoot a bisection beam that causes one half of your body to reject the other, ignoring durability. She later learns to make her force-fields explode when hit.

Shiki Tohno (Tsukihime): Also notably a protagonist. Shiki's Mystic Eyes of Death Perception allow him to cut across someone's lines of death ignoring all durability and defenses. They prevent regeneration by killing the concept of you and can even kill abstract entities. Unfortunately, the user's durability is only that of a regular human.