Suggested by Man1cmanMario
Doomguy has all weapons and permanently-obtainable equipment from all of the games with the exception of the two artifacts from DooM 3, though he has the one from Ressurection of Evil.
This means he even has the Unmaker and BFG 9K (and a full 600 cells). Samus is in her Other M incarnation (which is pretty much Super Metroid Samus minus the Hyper Beam but with an extended blast radius when she shoots).
Battlefield, it is the map “Ascension” from Halo 2.
There are 2 backpacks for Doomguy at each end of the top level of the map. He starts at 200 health and 200 armor, if that can make any difference.
Samus can’t use Crystal Flash, but retains 6 energy tanks.
She has as many missiles as her enemy has rockets in his first game (in this match, he starts with max ammo on everything; she has max missiles and bombs)
She has 1 power bomb
There is a two-time missile recharge station for her where the banshee would normally be.
She does not have the beam that passes through inanimate objects (can’t remember the name).