As for OP, it depends on how generous you are with scaling.
Chaos calced Luffy dispersing Raigou at country levels iirc. If you don't think of it as an outlier, they prolly stop at Enies Lobby or so since peeps there would scale to that + would have the necessary speed to blitz.
Otherwise they stop at early post-TS characters.
In Naruto, they should get to Kage levelers prolly. People with barriers and sealing jutsu should be able to deal with Muso Tensei. Iirc the former even stopped people like Dan who was intangible.
In Shaman King, they should stop at post-Hell training Yoh or so. He's also Island level and has the hax to deal with Muso Tensei prolly.