Mewgenics' developers made one of my favourite hardcore platformers, and you can grab it right now for less than $4

The End is Nigh is effectively an unofficial sequel to Super Meat Boy: it's a reflex-oriented platformer with quick deaths, quick respawns and very dark humour. Protagonist Ash "flops his way through a future of pain and suffering" in search of a friend whose body parts are spread around a spike-filled hellscape. Collectibles are tumours.

I think The End is Nigh is better than Super Meat Boy, and while that might be controversial for some, I doubt anyone would argue it's not better than Super Meat Boy Forever...