Fishbone D

フィッシュボーン D

Fishbone D was the first Hollow Ichigo Kurosaki ever fought. Fishbone D attacked Ichigo's family in search of him. Ichigo had no choice but to accept Rukia Kuchiki's offer to become a temporary Soul Reaper. Ichigo ended up taking all of her power and became powerful enough to kill Fishbone D. So, by technical terms, Fishbone D was the first Hollow to start Ichigo's time as a Soul Reaper.