I go by with Saturn, Capricorn, and hard aspects like Square and Opposition. That also seems like common knowledge among us astrology lovers and students anyway. But with the signs? I think every single sign is capable of expressing those negative energies such as self-hating, self-criticism, and etc. Maybe the reason why some people seem to pick certain signs as more prone to depression or low self-esteem is because of the nature of the signs. Like water signs, for example. Emotional, receptive, flowing in their own ways, but also deep and intense.
Pisces, from what I've observed from other people in my life, seem to be the most open out of all the three. Most forgiving, most naive, most spiritual, most "watery", most elusive, most mysterious (yep, I think Pisces beats Scorpio in this one) and also the most sacrificing. IMO, I think Pisces is at the top of my list of which signs are prone to such. Next would be Scorpio, then Cancer. Cancer is a great sign, actually. It's a Cardinal sign, like Capricorn. Cancer can definitely combat these negative energies but that depends on the signature of the natal chart too. The softness of Cancer is very admirable IMO, and like its opposite sign, they definitely have some strong qualities but its more hidden.
The thing about Scorpio is that this sign will always express itself in EXTREMES. They can either be really up there, like the Phoenix emerging from a powerful transformation, or they could reaaalllyy down there, at the very end of a dark pit, and since this sign naturally embodies the darker themes of life, they can stay down there for eternity. So in comparison to Cancer, Scorpio has more...er, potential or more prone to those negative expressions. At some point, they can also be stronger, like incredibly strong. Because of the transformation that the planetary ruler of Scorpio, Pluto, can give to the chart holder. I'm referring to the good kind of transformation. I find this really amazing.
But Pisces, oh dear. IMO, Pisces people are the ones who look and seem like they can be taken advantage of. They're even more receptive to pain and suffering, and Neptune rules this sign. 12th house rules this planet. Correct me if I'm wrong, but isn't 12th house about the subconscious? About dissolving and fogging whatever it is that's in your 12th house? Like Sun in 12th house. Sun is about your ego. Won't that mean having almost no ego? Or that your ego is too foggy to be seen or discovered with clarity? For instance, i have Neptune in the 1st house. My self-identity has always been vague and confusing. Some people have told me this planetary placement makes me seem like a chameleon. Because I'm adapting so many expressions and idenitites throughout my life, I was never certain of who I was and what I want. Other people too, always have different views of me, but they never really saw who I am deep down.
So with that in mind, I think that could contribute a lot. I have a friend who has Moon-Venus in Pisces, exactly conjunct. Extremely forgiving, open and sacrificing. He actually drowns himself in his sorrows, and he actually loves it (even though he denies it). Like, he seems to be unconditionally loving his friends and love interests that he doesn't keep them with him, allows them to hurt him, very empathic to other people's emotional hurts, and also... depressed. He noticed this (and sometimes, he doesn't) and he hates himself for it. He wishes he had guts to push people out of his life and improve his self-esteem for the better, but he's too... kind. :/
And theeen, put in some Saturn. Haha.
I agree with Blackempress. Psychologically, the angular points of the chart are very important for the psyche of the hart holder. I personally emphasize the 4th house and 10th house axis. I have Saturn down there in my 4th house. Saturn is opposite my Sun-Venus, in which they are up there on the 10th house. I have T-squares that involve those two houses with my 1st house planets. I'm carrying a lot of inner conflict that came from my early experiences/childhood, and my parents were like the starring roles of those hahaha. As a result, having a weak inner foundation made me crave for acknowledgement and recognition from other people. But since people have put me down on this too, it fueled my frustration, and voila! Self-hatred filled my mind and heart haha.
I'm also aware that people who have harsh aspects to Saturn to their personal planets can develop that "I'm not good enough" complex, and this also fuels their self-hatred all the more. I have friends like this, and they mirror me too. And maybe its not just the Saturn aspects though. I think we should all look at the chart as a whole to see many possible influences that contribute to this.