Ride a Honda CG125 with a little 12 Horsepower motor, it's a prime example of an underpowered motorcycle!
Anyhow; 'underpowered' and 'overpowered' are 'generic' vocal terms. They are not benchmarks!
The Honda CD200 with a ~15 Horsepower engine is an 'overpowered' motorcycle for us Pakistanis, whereas to most Americans; even The 50 Horsepower Suzuki GS500 is 'underpowered'.
So; the very definition of these two terms depends on the 'user'!
Hope it helps!