What would offend a Celt?

[General Appo]

Rape and kill his entire family (including male members, pets and husbandry animals, any servants and the occasional passer-by), burn his home, discredit his name to make him the laughing stock of the entire world and get him exiled from pretty much everywhere, turn his friends against him (and then rape and kill them just for the heck of it), beat him up and leave him alone completely naked in the wilderness, crush his private parts (not cut off, crush), breck his fingers, nose, toes and some various other bones, publicy torture him infront of a laughing crowd throwing tomatoes and passing water on him, have dogs rape him, slowly force him to eat parts of his own body, and then finally say something really mean about his mother. That usually makes them feel a bit insulted, though admitedly, it doesn´t always work.