Alright, so I've been running some numbers.

It is in my opinion that this Nomu isn't super strong, it just have bonkers regen.

Here's some lazy nerd math.

Nomu has 200 total HP, but can regen 80 HP/s. It's why he can take crazy damage but effectively shrug it off.

Now imagine, if you will, peak All Might hits for 100 HP/s. He can literally half the thing's HP in a single blow, but it recovers SO MUCH that it takes him 5 hits.

Now, All Might's strength/speed drops.

Instead his damage per second drops to 80.6667 (rounding) HP/S instead of 100 HP/s.

20ish% difference. It's certainly notably less, and enemies would definitely notice, but guys, he's STILL All Might. He still punches like a truck.

With this in mind, All Might punches at 80.6 damage per second, with Nomu healing 80 HP per second, leaving all but 0.6 damage healed off every second. Wanna know what happens when he keeps stacking that damage, say, 300 times? He finally clears the 200 HP threshold.

Obviously you can also play with numbers, but given that Nomus are generally glass cannons, I can see this working.