Haven't read the entire thread, but the first pages makes a thought strike me: So much offtopic. Can you guys please stop discussing the ethics behind sex and just answer the fucking question? Or at least qualify why your post is not offtopic? Omg
Personally I don't get of hurting others, but I do think it is a little kinky to be in a position of power - to slowly force the penis up to the absolute point of pleasure, and then a teenyweeny bit further, just to let the chick know whats at stake. But the ones I have done this on have all been game - if they werent it would just be stupid and offputting for both of us.
I have by accident found that if I have my girl laying on her side, and I lift up her leg (I am sitting up, entering from her rear), then if I insert it in an off-angle it will hurt a lot. So that is a position that warrants caution.
Laying in spoon I can get it all in and up and feel the boarder of joy
Any ways, these things depend on penis size, shape etc. paired with the girls size, shape etc., so there is no real saying of what is a bad/good/hurtful/pleasureful angle. Know your boo, that is all.