Which coins have been killed thus far? The reason I ask is because I'm curious: technological artifacts don't usually have the sharp line between life and deat

Which coins have been killed thus far? The reason I ask is because I'm curious: technological artifacts don't usually have the sharp line between life and death that most biological lifeforms do, particularly in the case of software which can potentially lie dormant indefinitely as a static bitstream. However it seems to me crypto currencies should have a sharp line, because as I understand it, the process of block mining serves as a heartbeat; the cessation of the heartbeat should serve as such a line. I'm wondering whether that is actually the case; what really happens when the heartbeat of a crypto currency stops?