Diddy Kong is far more agile. Bowser Jr., much like his father, is too slow and would get too tired too fast to beat Diddy.
Chihuahuaears
I was gonna go for Diddy until I remembered that Bowser Jr has more weaponry under his control than the USA military. Diddy has a jetpack that can only fly in bursts a few seconds at a time and a wooden gun that shoots peanuts. Do the math.
Haha
Diddly would win. Baby bowser would be nothing without his dad and so bowser jr can go cry to his daddy when he loses the match
M Enrique2000
bowser jr would win against diddy kong and then when diddy told his family it would be all out war on the koopalings and the kongs first these are 8 kids with armies the kongs would attack lemmy after that iggy koopa would come rescue lemmy then chain reaction in the end the koopalings would win
M Enrique2000
hands down without doubt koopalings would win
sol rael
diddy would just hit him 3 three times and its over