If it is not the result of mental illness, then yes. In Switzerland, you can go and legally end your life.

If it is voluntary, repeated, and the person of sound mind, I can't see why the government should prevent a terminal patient who is in constant pain from dying with dignity on their own terms.

Are there places where suicide is criminalized?

"Should suicide be allowed too? "

If we say that people own their body and their life - then yes, they can decide.