Not counting bugs and all that.
Dead Space, fully upgraded Plasma Cutter, which is pretty accessible to get before mid point, can carry you all the way through the entire game.
Bayonetta, in all 3 of them, your basic pistols, ANY hits you do to enemies will keep the combo timer rolling, if you pace your shots well you can keep a combo going for the entire fight phase.
Counter mechanic in Way of the Samurai, notably 3, it can be done with 99% of the playable weapons, easy to learn, can be chained if there are more than one enemies, and will 1-shot mooks without fail even in the hardest difficulty, bosses too if you've upgrade said weapon.
In SRW X, Gurren Lagann join your party pretty early, it's the only unit you got for a while who has a move with Barrier Buster effect, also it is obviously the strongest unit you ever gonna have here.
If you have DLC for SRW 30, Dygenguar, same reason as above, not to mention there are gonna be even more OP units later on.
Early Mortal Kombat, pick Raiden, teleport, jump away, uppercut, rinse and repeat.
Hitman, 47 is technically an unstoppable killing machine, limited only by whatever the game rules imposed to you. I mean nobody can stop you from killing every single NPC on every map.