These are the three criteria I think are important for an ideal suicide method, at least for me:
1. No permanent damage in case of failure
I remember seeing a (hopefully fake) video of someone who shot their face and jaw off with a gun and survived, turning him blind and without a mouth and nose, and basically visually transforming the poor guy into a grotesque monster. He picked a method that is seen as reliable, but he still survived, and his life will undoubtedly have gotten far worse after that affair, even if he got the correct mental health attention which he may have lacked before the attempt.
2. Light on pain
It should not be more painful than something like a migraine or twisted ankle, ideally it should be painless and unconscious.
3. Reliability
Note, this criteria is subservient to 1 and 2, and reliability does not have to be that high. If chance of death is only 10%, but pain is light or non existent, and there is no risk of permanent damage, the ideal suicide method lets you attempt as many times as you want without fuss, causing you to die eventually through chance. It's okay to let your mental anguish continue for a little while as long as you have hope for it to end soon through death. However, a higher reliability is still preferable and good to know when researching methods.
Conclusion:
Are there any suicide methods that meet these criteria? I doubt it, but I'm curious. I'm also curious what you all think in general about desirable and less desirable suicide methods. I am researching suicide methods that are painless and low risk of permanent damage, because I don't want to make my life worse, and I'm a little reluctant about causing physical pain to myself.