The Fist returns fully in Doom Eternal. Uniquely, and unlike for Doom (2016), the Fist is always available, but is accessed by pressing the "E" key rather than selecting a weapon from the number keys.
The "E" key can be used as in Doom (2016) as the Use key (indicated by a message "Press E to Use"), or to perform Glory Kills if a monster is stunned (indicated by flashing blue or orange as in Doom 2016), but unlike in that game, "E" can be used at any time to punch an enemy if it is not stunned, as well as to punch damaged walls to reveal secrets, or other things to perform tasks.
The Blood Punch is Doom Eternal's replacement for the Berserk Fist, with a similar power as well as ability to damage multiple enemies. It is accessed by performing several Glory Kills, and is discharged by striking any enemy that is not stunned.