First the difference between suicide and Christ and Christian martyrs is that they sacrificed their lives for God, in my opinion something that is very different than suicide. Suicide is taking your life because of pain or shame or guilt. I'm a christian (not catholic) and I don't know about suicide... does God really send you to hell because of it? That's up to God no doubt, but I think he's against it because he created this world, this life for us and suicide is such a selfish act... it takes a your life, which God gave to you, and it hurts so many people around you.
I think that each situation of what we see as "suicide" is different that God is the only one who really knows what's going on, what's inside your head, what you want, God my be one who serves justice, but we can't forget that he is also merciful... and he knows pain too... he let his son be tortured and killed.

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