Being imperfect is a good thing, because it means you have room to grow.
Tell me what you think about this:
Luffy: flaw is the sin gluttony. Pursues fun and food. Not a responsible person.
Zoro: flaw is the sin sloth. Sleeps whenever not fighting, eating, training, or getting lost. Apathetic attitude.
Nami: flaw is the sin greed. Loves money and tangerines. Steals from pirates, steals from crewmates, blackmails crewmates, steals keys from everyone.
Sanji: flaw is the sin lust. Hits on girls. Crazy horny perverted fanboy of Nami and Robin and every hot babe in the world.
Ussop: flaw is the sin pride. Blatantly lies his ass off just for the hell of it. Thinks of himself as special and awesome. Attention seeker.
Robin: flaw is the sin envy. Always sitting quietly in a isolated area reading or watching people. Easily betrays crewmates.
Franky: flaw is the sin wrath. Short bad temper. Loud, obnoxious and a troublemaker.
Chopper: flaw is naiveness. Extraordinarily gullible. Absent-minded. Error-prone.