You don't remember your birth and Guts Killed the man who raped him, Kuma can't Kill the CD's
1) We are comparing the misery of their lives from the perspective of the reader so Guts remembering or not is irrelevant.
2) Killing the guy ain't going to magically un-rape Guts.
Misery inflicted is misery inflicted and no amount of physical vengeance is going to undo that.
And Guts only lost a few Friends whereas Kuma Lost Friends
So they've both lost multiple friends? That sounds about equal then.
Guts was born in the decomposing corpse of his biological mother, his step mother died a diseased death when he was young and his step father hated and abused him before selling Guts's shota booty to the aforementioned rapist, the revelation of which ends up with Guts having to kill his step father in a fight that banishes him from the initial mercenary camp that Guts could consider a home.
Yeah, Guts's parents aren't exactly around either.
he probably even Lost his wife
I can't work with a probably just to give Kuma an arbitrary "probably had it worse" award.
I can tell you that Guts's partner meanwhile got raped in front of him by his best friend Griffith, who decided to sell out the souls of all of his loyal subordinates (all of whom were Guts's friends and comrades) in order to be reborn as a powerful demon.
I sure don't recall Kuma getting backstabbed by his best friend that sold his soul out to literal demons and raping the woman he loves in front of him.
I will go with Guts as he couldn't even sleep for a moment
Amongst what should be a long list of additional reasons. Lol.