Personally, I haven't experienced grief from a suicide- only natural death but I imagine there are differences. And further differences between that and an accident or murder. I think regardless- when someone is considered to have died before their time- that could even be via a sudden illness- there is anger involved as well as deep grief and a sense of tragedy. Where that anger goes depends on the death. If it was an accident- culpability is often sought. If it's murder- then obviously, everyone can blame and despise the murderer. Even with illnesses- those so inclined to believe may feel anger at God. The obvious problem with suicide is that that blame falls on the person. Sometimes- you do sense anger in those left behind- 'How could you have done this to me?'
I expect sometimes- that's too difficult for them to cope with so- they blame mental illness, which could have played a part- obviously- but doesn't necessarily mean that person couldn't rationalise. Then they blame places like here and the company that sold them the method for enabling their loved ones suicide. They may even think their loved one was coerced- if they don't want to believe they would have made that decision by themselves.
Plus- there's guilt. We may all experience guilt if a long lost relative dies and we hadn't made enough effort to keep in touch with them. (I have that.) But, when it's a suicide- that person was obviously struggling. Those left behind are bound to be asking themselves- could they have done more to help? Could they have prevented it in fact? That can't be easy to live with. Not that it solves everything but that's why I think it's important to leave a note to say that there's nothing anyone could have done- if that was the case of course.