if you view your profile and click on pending actions on the left, then click on the title of your run, the video page will show and there's three dots on the right side, click on that and delete

The strat that I use for that fight is to shoot out the eyes, knife him from behind making sure not to hit too far into his center so you don't hit his weak spot (he'll recover early if you do). your first knife should break, continue with second knife. when he starts getting up, switch to flamethrower and flame him until a bit after he roars. Then shoot all the eyes again, do the same behind the back knife strat until the second knife breaks. then throw a grenade (2 if you have an extra) then back to flame. He should die before the final phase. This is for 120FPS, I haven't been able to get the quick-kill at 60FPS, but it is possible, especially with extra grenades. But even with this strat at 60 you can kill him immediately after he throws the large section.

Ok, thanks for the answer!

Do I need to delete my old run after submitting a new and improved one? Or will a Moderator delete my previous record when they approve the new one? Just wondering what the etiquette is. Thank you.