Tien > Krillin > Yamcha >> Chiaotzu > Yajirobe >>>>> Videl > Hercule
At the end of DBZ, probably.
And yeah, Yajirobe was on par with Goku during his introduction. If he was more serious about training, he might've been one of the strongest humans! Funny that he accomplished more than Yamcha ever did, though.
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"I wanted to change the world, too. But I changed nothing. That is my story."