my butt and legs are blessed by genetics, if you consider being built like a fire plug "blessed".
However, I have done a ton of
step ups (both from the side and from the back of the step)
static lunges with back leg elevated
side lunges
sumo squats
box squats
kick squats
plyometrics
...for years. Not with super heavy weight. Most weight I've ever used for step ups, lunges, etc is about 40-50lbs. usually 1/2 that, with high reps and lots of pulses at the end of each set.