Seaman was a decent character on Yu Yu Hakusho.
He was radicalized by Shinobu Sensui, and had the power to create a monster that existed in another dimension. After capturing Kuwabara and his friends, he’s almost successful in killing them all.
Until Kuwabara awakens his spirit power to bring out a new sword that could slice through dimensions.
He should have been killed, but the good guys let him live. They convinced him that there is more good to humanity than what he saw in the Chapter Black tape.
So he agrees to help them take on his former boss.
And he did almost nothing besides inform them of certain information.
He survives but gets knocked out by a member of the Spirit Defense Force. He was a bit of a wimp, but I found it hard to hate him, maybe it’s the pity I feel for him.