As others have said, ‘primal’. Others have focused on the orgasm but I find it hard to separate it from what’s gone before. She’s let you inside her, in some cases trusted you and allowed you to bareback, and you’ve ploughed away making her scream and writhe. She’s begged for it harder and faster but you’ve held back on your own pleasure to make her cum just one more time.
Now it’s time for your reward. You no longer need to worry about passing the PONR, and she’s fully wet so your size won’t hurt her. You let loose and just drill away, faster and deeper than before for one final finale. She senses the gift you’re about to give her, draws you in more closely and screams for it. You’re now past the PONR and that it’s only seconds away. Then it hits you, electricity from your cock and then through your whole body. You unload, sending her into one final orgasm herself. After the last shot, you stay deep inside and embrace. If you’re trying for a kid it’s extra special as you hope you’ve bred her and done your duty as her stud.