JDKKiller is a piece of software that runs in the background and force kills the JDK process whenever Fusion is closed. This is done to prevent Steam from thinking that Fusion is still running
It's recommended that you use Android Studio's JBR for exporting your Fusion games, because using a separate JDK install can cause issues (e.g. kill your Minecraft process).
JBR can be found in Android Studio\jbr