When villains like Electro are written properly:
That wall crawling shyt falls apart rather quickly. There's a reason why Magneto tried to recruit him to the Brotherhood.
With that being said:
Spidey does indeed hold-back. A lot.
Most of the guys he deals with would be left a bloody mess if he cut loose. Only the guys in his weight class (Green Goblin, Hobgoblin, etc) or above could take his unrestrained punches.
yeah I've always said Marvel constantly lists Pete as Class 10, and that's fine for when he was 16.
He's prolly a legit class 25 or 30. No "training" needed, cause honestly the only marvel hero that stays in the trenches more is prolly Wolverine.