Captain Levi is the best character on AOT
Seriously he is a kick ass character.
Because a rotting undead corpse is probably a better choice than most politicians
Isayama consistently makes him the strongest character in the series without question. Whether or not that makes him the best is up to the individual. If ability to kick ass is what does it for you, then he is easily the best character. I'd imagine Mikasa and Annie are up there for you too.
If you can allow yourself to let his back story sink in, then he becomes one of the best characters for much different reasons than his strength and ability in battle.
🐺 "The North remembers"