I think this should be an easy win for Izuku. Gumball has an immense amount of hax, but he never uses them in combat, and even with The Console (it wouldn't even BFR Izuku or anything; when Gumball activates it,
Gumball gets sucked into the game as well), Izuku is still strong enough to quite literally beat Gumball into submission. The strength gap should take care of Gumball's regen. Plus, Izuku is way more agile and has superior stamina to where he could dance circles around him.
I don't think I need to go over the skill and experience advantage either, since Gumball tends to run away when placed in a fight (plenty of examples on his profile), as well as how his daily routine is go to school, cause trouble, have the occasional odd encounter, and go home. That's nothing compared to literally going to a school for future superheroes and fighting criminals that eclipse anything Gumball has faced (including Rob). Running away and hiding won't do anything anyway, since Izuku is no stranger to dealing with opponents trying to hide from him. In fact, when he was still a noob at using One for All, he dodged Bakugou's surprise attack.
At first glance, Gumball's helmet may seem like it'll be an easy win for him, but it's important to note that
it can still get knocked off with ranged attacks, and since Izuku is no moron, he's eventually going to take notice of this assuming Danger Sense or the past wielders of OFA don't beat him to it. Also, ranged attacks are what Izuku has plenty of; that's kinda his thing anyway (gusts of wind >>> throwing mud). In fact, with Gumball being armed to the teeth here, that's basically a one-way ticket for Gumball getting temporarily blinded by Smokescreen.
On the topic of Izuku not being a moron, is he really going to politely let Gumball write something down in the Magic Notebook in the middle of a fight?
By the way, I should've mentioned this earlier, but I've noticed the threads where Gumball has won (Peter, Jotaro and Johnny Test) had him in-character, and he won via hax, but...uhh, the arguments there won't apply to Izuku.
- As I said, Izuku isn't going to let his opponent randomly write stuff down in the middle of a fight. Plus, Gumball only utilized the notebook to reverse the effects of Sarah's fanfiction (never thought I'd type those words), so it's questionable to guess that Gumball would write down something like "My opponent stopped dead in his tracks".
- Fusing with Izuku is out of the question, as Gumball only used it to lecture Anais about parasitic friends. Besides, Izuku has many ways to keep out of Gumball's range, like Air Force and Black Whip, which, again, are kinda his thing.
- Gumball's Explosion Manipulation? Yeah no, that's not durability negation at all since it only affected 9-A characters. Izuku could easily dodge it too, since the Explosion Manipulation requires Gumball to run up to his opponent.
- Gumball's death glare is so close-range that by the time he would think of using it, Izuku would've already analyzed him and figure out a way to outsmart him, which, given the intelligence gap, should be a walk in the park for Izuku.
tl;dr - Izuku takes this. A lot tougher, would have no issues analyzing Gumball and his equipment, and is leagues more skilled/experienced and smarter.
Also, these are all assuming Gumball doesn't start the fight by underestimating Izuku
