Even if the Fantastic Four could harm him, Doomsday is capable of adapting to damage and injuries. In many versions, Doomsday can't be killed the same way twice. In the famous "Death of Superman" ...

A character that had a major role in the Arrowverse got another chance to prove themself in a different DC franchise.

James Gunn will never allow the darkest DC animated movie to be adapted into the DCU, despite its 100% rating on Rotten Tomatoes.