I don't think this riddle has anything to do with anything else. It can't be a normal character because characters are dependent on stats, the only character you can find as easily, that's within ruins is yuffie. As Wutai is classed as Wutai Ruins. and no normal character has a master. <--- reread this bit. It CAN'T be a character because strength is variable due to weapons and stats. A character can't be stronger than any others.
But if we're on this.
I believe it might be tifa, and her Premium heart ultimate weapon.
I look stronger than you look <--- This could be in reference to the fact when she punches they look forceful and powerful.
though my master are not <--- she's female, so she looks weak but don't judge a book by it's cover lala.
I hit harder than anyone else <--- this reference could be to the fact she actually hits and not slices or throws or bites etc.
though it's weak <------ could be the fact that gloves can break easily?!
I can be gained easily than you think <----- you just go to the wall market when you have the key to midgar and you get it in the item thing
though I seem to live in ruins <---- well come on, wallmarket is ruins.
