Let's hear them. I'll start:

Seymour and Vincent. First I love using slightly underrated characters. And these two fit the bill and complement each other nicely. Seymour needs the enemy to be debuffed to get his bonus damage. Vincent likes to debuff the enemy while also buffing himself, bonus that he does a lot of damage before debuffs.

Ideally, you'll want to use Vincent's Thunder attack first, followed closely by Seymour's Atrophy Spear. Then a second Vincent Thunder attack will just do massive damage (currently around 8k in this leviathan event). You don't even need a dispeller to remove their buffs, just push them off. Both of these guys hit extremely hard thanks to their synergy, and the bosses mostly tickle (magma breath does under 200 damage)