The above question may seem to have an obvious answer, but in all reality, and honesty, contrary to what one may want to believe, suicide is definietly not painless.
It perhaps is one of the most painful things one may have to endure in their lifetime. From its inception to final breath, there is nothing dignified, comforting, peaceful or serene about suicide for the individual or those who are left behind to endure the aftermath.
Those who are contemplating suicide, or who are knee deep in the very act itself, will understand that there is suffering and excruciating pain that can be likened to the most inhumane of poisonings and tortures. It is not something that is looked forward to, and most would tell you that they wish they could have stopped before they started. The physical pain is more unforgiving than any emotional tear upon the human heart.
The ones left behind have not just mere struggles, but a life time of unyielding patterns of guilt, fear, doubt, anger, torment and anxiety that seem to worm their way into the physical body that not only tears, but penetrates deep within that asks the question if they should be better off suiciding as well.
Anyone that tells you that the suicide ended peacefully is only stating the obvious; peace is achieved at death, not before.
Overdose is often a mislabeled term in the case of suicide. By definition it simply means to take an excess amout of drugs without intention. Poisoning however, is the intent to take drugs, poison in excess or any dose that is lethal for the sole purpose of killing.
Ask any doctor about ingesting poison and they will be the first to tell you that it is excruciatingly painful and does harm to most vital organs. And where death is the only and final outcome, it is never painless, one dies a slow, horrible, undignified death.