Koichi is invincible at Shiritori.
You have nothing when it comes to enemies. Why? It's not because you're super kind and everyone likes you. No, it's that you've defeated anyone who's tried. You are unrivaled and invincible.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.