hmm... the stackexchange link you posted has a top answer that seems pretty straightforward to me. I will try to rephrase it to (hopefully) make it clearer:
"butsu" means to lightly spank, to swat, or to smack someone/something gently,
as in a tiny, open handed swat. It doesn't have to be on the butt, and doesn't
necessarily cause pain.
"tataku" most commonly equates to "hit" or "tap", and in the case of 尻
it means to give someone a spank, or many spanks. But you also use this particular
word when talking about hitting inanimate objects, such as drums, doors, desks, and so on.
殴る is the most violent of these words, and means to punch or strike someone/something with a fist or hard object. Using this word implies an intent to cause pain, injury, or damage.
There are further nuances to these words, but these are the most common, and the ones I'm most familiar with.