This is level 13 of the Way Back.
(Note: Parts 8-16 of this tunnel can only be played with the Duplicator, so he will be the only recommended character.)
The trickiest part of this level is the very beginning, where you are instantly launched onto a long line of Crumbling tiles. So, what you must do is immediately jump off a duplicate to get onto a green platform, then try to beat the rest of the level without touching the Crumbling tiles. This is because most of the Crumbling tiles are connected to the chain that you land on at the start, and soon fall away.