I am going to show videos of Super Meat Boy. The main part of the walkthrough is getting the achievements that players receive when they complete the main 20 stages without dying. I will complete as many chapters (light and dark) as possible. These will be Iron Man achievements (Meat Boy only, except for Bandage Girl in Cotton Alley). I will follow a few of my own rules.
1. I can only use Meat Boy. If I ever get the Girl Boy or Impossible Boy achievements, they will be done with Bandage Girl.
2. I must complete the stages in sequential order. (Stages 1-20, in that order only).
3. No exiting the stage and starting that stage over if I am about to die. (The game will still give you the achievement if you do this.)
The warp zones, glitch stages, and boss stages are recorded separately from the main 20 stages. It would take far too long to complete all of that without dying once, especially by chapter 5.
Getting the Wood Boy achievement is not really that difficult, even if you are only using Meat Boy. You can't even die in the first several stages. It took me about 5 recorded attempts to do this.
Difficulty in getting the Wood Boy achievement with only Meat Boy: 1.5/10.