Come now, he's like the third strongest human, and the strongest (Krillin) said at the time that he would have been killed by the saibaman kamikaze too if he wasn't alerted to it by Yamcha's death. Also, it's not like that is in the same dimension as where he is by the end of Z, let alone where he gets in Super, since Dragon Ball is the worst media in the world when it comes to "number go up" power creep.

the saibamen, which are literally just plants that can explode

they're a powerful race of unstable alien plant dudes that freeza's soldiers carry around as backup because they're really strong

Cell Jr which is basically just a stronger saibaman

they're literally as strong as cell himself, they just don't seem to be as refined in technique

that means that until gohan got big mad they were roughly tied for strongest lifeform the universe had ever seen (until later arcs retconned that)