The Suicide Bomber is a role that can kill another player during the Day in exchange for killing themselves at the same time. There is nothing that can stop the Suicide Bomber's death when using this ability.
Suicide Bomber is not necessarily anti-Town, but it has been Mafia-aligned in practice. A Town-aligned Suicide Bomber is generally called a Kamikaze.
Suicide Bomber's ability has been seen as a Night action. However, this may impact its power considerably.
It is not unheard of for a Mafia Suicide Bomber to also be a Mafia Traitor.
Use and Power
A Town-aligned Suicide Bomber's effect is not dissimilar to replacing a Day/Night cycle in a single-scumgroup game, as both the Bomber and the cycle cause two players (one of which is more likely to be Townie) to die. The difference is that no other power roles get results in the Bomber's case.
Mafia-aligned Suicide Bombers are best off not looking for reasons to use their power, as one-for-one trades with the Town are usually slanted in the Town's favor. The major instances a Mafia Suicide Bomber would want to detonate are the events where the Suicide Bomber is about to get lynched anyway, or where the Mafia wants to kill a Town power role that is securely protected from the factional kill at Night (due to the interference of a Doctor, for instance).
In both cases, the value of Suicide Bomber is somewhere between low and moderate at best.
The Suicide Bomber that kills at Night is even weaker due to the potential for a protective role to stop the Suicide Bomber's victim from dying. The Suicide Bomber will still necessarily die, though, causing an utter failure that will be talked about for months to come.