Copy/Pasta.
1. Do NOT reply. Press "hide".
2. If you choose not to hide, then at least wait until he has posted enough Avatars, then report each Avatar post one at a time (he will insert random "hurrrr won't work generic pic" but as any Bant original will know, avatar fags like Agumon get banned here all the time).
Tldr: do not reply, simply hide.