As someone mentioned GrimeFigher I checked the menu "tools", but only rescue medium was listed as active.
Sandbox, firewall and safezone listed as optional items (showing plus symbol with green background when hovering over it).
Then I checked "programs and software" in control panel, clicked Avast and "deinstall/repair" and (surprise, surprise) GrimeFighter was checked!
Unchecked it, run setup, reboot and the revenant bcdedit.exe is gone!