Not possible at all to my knowledge. When a player dies, the information goes into chat in two separate forms: the first is the damage (Player is hit by Soandso's Whatever for ThisMuch type damage). The second is the kill message (Soandso has killed Player).
One of the issues is that those messages are not connected at all; the only thing that lets you know what killed a player is the order: what killed them is probably the last damage they took before they died. You can get an idea of what is killing people using a parser like ACT, but there's nothing as simple as what you're asking for.
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