Of course everyone has some motivation: Malen may be responsible for the raiding of innocents, but he was 'just' ruthlessly willing to eliminate whoever stood in his way or threatened his power. 

The purest evil I can imagine is someone whose motives are predicated on, whose pleasure requires the death and suffering of others. This is why I regard Hitler as more evil than Malen; but on a smaller scale, it applies to every abuser, tormentor, or murderer who gets off on suffering: famous names that leap to mind are Albert Fish (Google his letters for nightmares), John Wayne Gacy, and similar celebrities. 

An honourable mention goes out to those who, while perhaps not motivated by cruelty, manage to dehumanise others to a degree that lets them commit atrocities so grotesque that it beggars imagination. Unit 371 stands out, as does Christopher Columbus:

Columbus supervised the selling of native girls into sexual slavery.  Young girls of the ages 9 to 10 were the most desired by his men.  In 1500, Columbus casually wrote about it in his log.  He said: "A hundred castellanoes are as easily obtained for a woman as for a farm, and it is very general and there are plenty of dealers who go about looking for girls; those from nine to ten are now in demand."

He forced these peaceful natives work in his gold mines until they died of exhaustion.  If an "Indian" worker did not deliver his full quota of gold dust by Columbus' deadline, soldiers would cut off the man's hands and tie them around his neck to send a message.  Slavery was so intolerable for these sweet, gentle island people that at one point, 100 of them committed mass suicide. Catholic law forbade the enslavement of Christians, but Columbus solved this problem.  He simply refused to baptize the native people of Hispaniola.

On his second trip to the New World, Columbus brought cannons and attack dogs.  If a native resisted slavery, he would cut off a nose or an ear.  If slaves tried to escape, Columbus had them burned alive.  Other times, he sent attack dogs to hunt them down, and the dogs would tear off the arms and legs of the screaming natives while they were still alive.  If the Spaniards ran short of meat to feed the dogs, Arawak babies were killed for dog food.

Every human being has some evil element in them. It's part of living in a broken world. Some people may resist that evil in themselves more or less, and some don't. Everyone has the potential to become that sort of person.

There are some people who simply like to cause suffering for it sown sake. I haven't met anyone who did that per se, but I have met jealous people before, and that kind of person, in my experience, is the most likely to cause someone hurt. When someone else has something that you can't, like influence, or good looks, or a relationship with a particular person, your jealousy can drive you to hurt them - even when it does you no good. It might be minor things, like going out of your way to spread a lie about them, or inconveniencing them in some small way - but it's the same evil motivations, even if the acts themselves are small. That's what a lot of evil looks like: trivial, every-day things straight from the pit itself.

People succumb to the evil in their hearts all the time, on very different scales. It doesn't have to be this way, and there's hope for escaping that evil - as long as you still cast the sideways glance at your friends and neighbors, there's still that jealous little worm gnawing on your thoughts, deep down.

Yes since evil is about morals I know many people that don't share my morals and ethics.  By definition they become evil.  The more they stray from my morals the more evil they become.  For example racists bigots channers I consider evil.  Racist bigots the justify violence are even more evil.  Racist bigots that commit violence are even more evil than that.   All the while those people would think I'm evil because I don't share their bigoted views.

There are those that we classify as Schadenfreude.  I've met people like that.  While in the military these are the people you want to stay away from because when things go bad these people are worse then the people you are fighting against.

So ask yourself again, is Malen really bad in the grand scheme of things?