Clear Note of Zatch Bell runs this gauntlet of characters from One Punch Man
1. Beefcake
2. Mosquito Girl
3. Carnage Kabuto
4. Sonic
5. Sea King
6. Genos
7. Tatsumaki
8. Garou
9. Boros
10. Saitama
who is the strongest one he can beat?
Clear Note of Zatch Bell runs this gauntlet of characters from One Punch Man
1. Beefcake
2. Mosquito Girl
3. Carnage Kabuto
4. Sonic
5. Sea King
6. Genos
7. Tatsumaki
8. Garou
9. Boros
10. Saitama
who is the strongest one he can beat?
Effortlessly squashes everyone up to say... Tatsumaki?
She's shown problems with effecting suitably strong bodies and Clear is stupidly strong, so he likely just vapes her without too much trouble but she should be able to get his attention.
Garou likewise just gets hit with repeated AoEs until he goes down. His lack of range game is going to hurt him here.
Boros... could be too much. He's got regen, absurd strength and energy attacks as well. He's... essentially Clear's direct analogue in terms of loadout and they're not too dissimilar in terms of power levels all in all. Given that, I think Clear can take it just because he's more durable and his energy attacks are kind of more potent beyond Boros' biggest attack. Plus, he can always transform. He'll have to work for it though, work for it hard.
Saitama hits him and he dies because Saitama casually monstered on Boros who could give Clear a decentish fight. Saitama's power is still a big question mark because we don't know how far up it goes.
Tatsumaki's a beast, but I don't think that she's yet shown anything in the same league as Clear Note's casual mountain busting level offensive ability (and at least comparable durability), especially since he is many times faster than Tatsumaki had ever shown herself to be.