Naruto
Naruto ranks highly for difficulty because it combines 5 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
The hardest franchise modes are usually the ones with deeper rosters, wider year spread, and more overlapping character traits. Those conditions create more plausible candidates per guess and make late-game elimination much less forgiving.
Naruto ranks highly for difficulty because it combines 5 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
Hunter x Hunter ranks highly for difficulty because it combines 4 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
My Hero Academia ranks highly for difficulty because it combines 4 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
Demon Slayer ranks highly for difficulty because it combines 4 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
One Piece ranks highly for difficulty because it combines 4 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
Fairy Tail ranks highly for difficulty because it combines 3 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
Re:Zero ranks highly for difficulty because it combines 3 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
Spy x Family ranks highly for difficulty because it combines 3 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
Bleach ranks highly for difficulty because it combines 3 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.
Death Note ranks highly for difficulty because it combines 3 characters with enough year spread and trait overlap to keep multiple candidates alive deeper into each solve.