Kirb

This fucking bastard is so well written, such a tragic character to be honest
I always loved him, but having played Undertale Yellow and seeing how much justice they did him made me think properly about him again.
Also I see him as an adult who never had the chance to actually grow up mentally properly due to obvious reasons, he is a literal man-child traumatized by his cruel form of immortality and godlike powers, which makes a lot of behavior make so much sense
As a final comment, my head-canon for his voice would be Josh from the Snapcube Live Fandub of Until Dawn