Suicide : The word means an action of taking one's own life deliberately.The word is a noun and not a verb. It can be used as an adjective also. For example: The suicide bomber attacked the hotel and killed many innocent people. 'Suicidal' it is also an adjective . It means self-destructive .
I have come across people saying: He has suicided. It is not correct. The correct form is -He has committed suicide.
When you use 'suicidal ' you are using it as an adjective. For example; His suicidal nature is worrying his parents.
After the results of the final examination, some students commit suicide because of humiliation.
The abashed model committed suicide unable to face the world.
Mary made suicidal attempts when she lost her job.