I know someone whose brother killed himself 35 years ago, because he was mentally ill. He's still not over it. He wonders every day what he could have done differently and works 5 to 6 days a week as a therapist, hoping he can prevent at least one person from this happening to them.
Suicide isn't the answer, even when it seems like there isn't an answer. It leaves people hurting forever with questions they can't answer, even if they devote their entire lives to the subject.
Believe me, I understand wanting the pain of depression to end. Mine ends sometimes, for a while, but I still slip back into the dark and want it to be over. I would give my life so that others wouldn't hurt, but I realized something, I'm not that important. So I suffer on, with that tiniest flicker of hope that it will lift again and I will feel better if only briefly. Besides, there are so many people I don't want to leave hurting; my kids, sisters, brother, grandkids, nieces and nephews, and some others.
If you've gone that dark, please call someone to help you get to the help you need, be it your psych team or to a hospital. You're sick and need help and it's an emergency