Shiryu ofc.
He is not an admiral level guy but he's should be stronger than other yc1 guys.
Before his df He was maggelan's equal who beat iva (second strongest under dragon) quite comfortably, that alone make him yc1+ imo.
The whole scene with garp only make him better.
He knew that garp will protect Coby and capitalize the moment in the best way possible.
He showed speed, lethality and brains in one instant.
I don't agree with people saying that zoro needs him in order to train his coo if it's not for fs ofc.
In the battle zoro has amazing coo feats that surpasses many characters, even coo specialist.
Whatever the case shiryu is an excellent character for zoro as his next serious fight.