Hiei and Kurama are among the strongest demons.
Kuabara is the strongest human.
Yusuke. lol. Don't need to say much about him. He could probably solo Ichigo and Luffy at the same time. Yusuke is smarter. He's stronger. He's probably not faster, but his spirit awareness was super high at the end of the series, so Ichigo's shunpo wouldn't do much.
Goku could kill them all though.
Yusuke's crew vs Straw hats vs Team Ichigo vs Goku, Vegeta, Gohan, Piccolo, Goten, Trunks....
DBZ would pwn everyone.