anyways, I'm voting Denji
Their AP gap is like 20%, and although Ellen does have crit dmg buffs to make it higher it's not gonna affect much
Their skill honestly shouldn't be much different either, Denji fighting devil his entire life isn't much different than Ellen fighting Etherials for work either. Denji has been fighting for longer probably but it's really not that much of an advantage, especially since this is Pre-Training Denji
Ellen's freezing ability doesn't really perma-incap Denji cuz if he hits him again he procs Shatter, which, although it causes an additional burst of damage, would just break him out of the freeze. NOT hitting him means he just thaw out after a couple of seconds anyways cuz of how her ice works
So for the most part they're dead even and would jut be slashing each other until one of them dies
except Denji has significantly better stamina and pain tolerance even without considering his regeneration. Ellen's stamina is notoriously bad due to her poor school/work balance, and is forced to carry around candy in order to give herself short bursts of energy. Even small skirmishes can
make her pass out from exhaustion Denji, on the other hand, is significantly more overworked due to his lifestyle, barely eats food at all, and still has more than enough energy to mow down devils day by day. His pain tolerance is also obviously insane compared to Ellen, who has literally no pain tolerance feats
IMO they just keep hitting each other but Ellen tires out far quicker even though she's doing a bit more damage