On the subject of knockback:

In many old style platformers, knockback has a pivotal core role: making the level hazards just that much more dangerous, and punishing those who push forward without caution.

This, of course, leads to many frustrating deaths.

Or hopeless situations.

Knockback isn’t always bad though! At least, if you know how to use it. Abusing knockback is often a core speedrunning strategy. (Also, look up Alucard death skip)

A more modern approach comes from Bloodstained: Curse of the Moon, where you can choose to play a harder mode with a bit of knockback.

Vs an easier mode without.

We are going to be taking a fairly similar approach to Bloodstained here, and more or less let the player select the type of gameplay experience they want. Of course, we still need to moderate exactly how much knockback we have during our Veteran mode in order to perfectly match the classic experience…

Ok, maybe not that much.