What is a step lighter than Deathmetal?

So for some context, me and a friend got into an argument recently after I said Groove metal and heavy Thrash were what led to death. She counterargued by saying Groove is not heavy enough to which I responded with The Great Southern Trendkill (the song). She said again that it can't be because "Metalcore" (not actual clean metalcore but more screamo) and Slipknot were heavier. I still stand by that Pantera and Slayer along other thrash and groove bands inspired what was to become death metal as we know it.

What I want to figure out is what is "heavier" between metalcore and groove aswell as what comes before death metal?

Edit: Worded poorly but I know death came before groove. I didn't mean to say it was what inspired it, moreso sonething that influenced it later on (in the 90's).