Maybe these two guys?
Takes place where the strong eats weak.
The blue one is sarcastic, cocky, rude and a bit mysterious. He belongs to a group that sucks the energy out of souls using their sword (you can name the group whatever you want). He wears earphones to block out the screams of souls that he's taken. The soul is used to make the user more stronger and faster.
The purple one is slightly quiet, reserved and very tactical. He works alone by silently and quickly killing souls. He has a tragic past that made him want power (you can make this up). He meets the blue guy and reminds him of one of his friends involved in the tragic event.
Also when the user is almost godly strong their hair changes to the color of their sword.
you can make up whatever I didn't mention, for example their names. I just made them so I'm sure I'm missing a lot of detail, can't wait to see the outcome though
3nodding