I'm not saying he's unbeatable, just a question! No manga or comic books. My friend, big O thinks Ramuthra can beat him, I doubt it.
If you don't know who sun Wu is
Sun Wu? The monkey king, so powerful that he went into the heavens and defeated the gods, so fearsome that he forced the death god into checking monkeys' names from the death list. Strong enough to pull the moon from the heavens and change his size and shapeas he wants to. He is Immortal and nearly unbeatable, a master of magic and battle, also a sly trickster.
Oh and he at the forbidden 桃子(peach) which grant the person who eats them immortality 100% immortality...he was trapped under a mountain of rocks for 800 years and came out 100% fine. he went into heaven and roughed up most of the celestial's except 玉皇(jade emperor) who is the ruler of heaven and earth (similar to LT) only answers to budah himself . so in essence to answer your questions i think only cosmic entities could challenge wukong.
Also goku was based off of Wu kong (he is very popular in Asia, kinda like superman here except he was made some thousand years ago). SunWuKong has an army of immortal monkeys that know magic and have skills in combat, he lives in a hidden mountain castle (behind a waterfall) where they have unlimited privacy. He looked for and trained with immortals for years. His power pole (sound similar to goku's?) can change shape and size for whoever can wield it, and it weighed too much for most people to weild, even the dragon king, but sun had no problem, as if it were a feather