Sun-Neptune
Moon-Neptune
Neptune means lack of boundaries and when aspecting personal planets it dissolves the self. When I say dissolve the self, I mean that the self wants doesn't want to have boundry's; it wants to be a part of something greater.
Sun-Neptune people struggle with being their own individual self or fundamentally don't understand how someone can fully be individual. They often lose themselves in other people or activities; they act as chameleons with no actual sense of self or purpose. They feel they are a part of greater purpose way beyond their actual self.
From a literal perspective, and if the native is on a negative path, this could make someone want to commit suicide because it's the ultimate form of self-abnegation. The completely dissolved self.
Not trying to glorify suicide here, but that's probably what goes through their mind. Suicide is the perfection solution to a physical living, individual, entity that sets boundaries because it's in its nature to be separate from a greater whole.
I think the square or opposition is more likely to make the native suicidal. Especially squares because squares force the native to make some kind of action to get the result.
Sun-Pluto
Moon-Pluto
Pluto is often associated with death and change. Something dies to make room for something new. So again, from a literal perspective, a person commits suicide because they killing off an old part of themselves (in this case their own body in this life) by reincarnating in a new body to begin a new journey. Because the life that they are living is probably redundant or worthless to either themselves or the people around them.
Although, I think this is a more negative side of Pluto. Suicide is usually a hasty and irrational change or death before someone has fulfilled their spiritual mission on Earth.
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I think Mars and Uranus transits are triggers for these Neptune/Pluto aspects for one to commit suicide. Mars is physical and makes someone take some kind of physical action; mars is also violent and so is suicide. Uranus isn't necessarily physical, but it generates random and shocking events. Suicide is usually shocking and often random because people don't expect it to happen.
