The final iteration of the onboarding level has the player practise movement mechanics: simple moving, jump/fly up, full throttle flight, and dash jumps, with a small parkour segment to practise the dash jumps. These are introduced step by step so the player can digest the different character abilities more easily. The dash jump is the most complicated, so I gave the player more time to learn it through a freeze frame and the parkour segment.
After the movement segment, the player meets the first enemy, which attacks from behind and activates another freeze frame that teaches the dodge and the perfect dodge mechanic. The player goes on to learn basic attacks and eliminates the enemy, which unlocks the next area, much lower down, to teach the ground slam, also through a freeze frame. The last area introduces the killzone, which the player can push enemies into to kill them, and the onboarding forces the player to perform actions that push enemies into it.
This version of the onboarding has been much more effective at teaching the mechanics of the game, thanks to all the errors and learnings I went through developing it.