Surely some philosopher somewhere has thought about a question like this: If someone lives their life in a way that causes constant tangible harm to all others in society, and someday is murdered by a person they harmed, did they commit suicide?

I'd say "Yes" using other examples of "accidental" suicides. Things we all basically attribute to the dead person's actions, acknowledging that while they should've and could've known better, they did it anyway and are now dead for it.

One easy example: Guy gets super drunk and drives his car home every night from a bar. One night he loses control, skids off the road at a high velocity, hits a tree, dies on impact. Everyone sort of silently accepts that he killed himself. Not necessarily on purpose, but his actions directly killed him.

Another example: Drug overdose. These are more directly often referred to as suicides with the added information of intentional or not intentional (not always apparent)

The argument against this would be "I'm treating the harmed person who retaliates as like a force of nature instead of a human being with agency." I'd say that's fair, but when you consider millions of people who could potentially want to retaliate, statistically there's gonna be a few who do choose to do so. That's not really a force of nature, but it is outside of human logic and agency to an extent. It's a predictable chaotic variable or something. A known known... not an unknown known. Perhaps an unknown unknown?