A simpin bug is a person who not only is a simp but also may cause harm (physical, mental, or emotional) to others in his path of doing so. Particularly whenever his friends call him out for it.
Friend 1:" Hey dude she doesn't like you just give it up"
Simpin Bug: "SHUT UP SHE DOES LIKE ME I KNOW IT" *pushes Friend 1 to the ground*