he fights all 3 admirals one at a time. who would he beat and who would he lose to?
They all have haki(i think) so they all can harm each other
But throughout the whole Marineford arc, the three admirals had not combined their power with haki for offense. They are not as skillful as Garp or the Kuja. On the other hand, Enel can tell what they are gonna do next and materialize before getting hit.
Actually Enel can hide and attack Kizaru with a long range attack and as for Akainu, Enel has a greater attack scale than him. Not to mention, Enel did burn through pure rock wall. The only reason Enel lost to Luffy was because Luffy was the main character and they need a happy ending. Enel would've burn right through Luffy theoretically speaking.
Enel has an amazing DF and he's no doubt powerful but the Admirals would likely win because they're more likely experienced with haki use. DF's count for shit against someone with superior haki. Take Mihawk or Shanks for example, two non DF users who can beat down pretty much anyone.
Although Enel wasn't really given a fair showing so it's hard to call. I'll have to do some research on this.