This is gonna be a long one. I'm using the weapons set from Halos 3 and Reach.
Multi-Kills: All the multikills from Double Kill to Killionaire. There would be a new multikill medal for every consecutive kill past Killionaire. It's called Serial Killer.
Killing Sprees: Alongside the normal sprees from Killing Spree to Unfrigginbelieveable, the multiplayer spree medal rewarded for every spree after Unfrigginbelieveable is Anarchy. Obviously any and all spree medals require you to obtain it without dying.
*Not faction specific
* Loadout spree: Get 5 kills with loadout weapons.
* Any Weapon: Get 10 kills with loadout weapons.
* Basic Bob: Get 15 kills with loadout weapons.
SMG, Assault Rifle, DMR, Battle Rifle, Magnum, Plasma Pistol, Plasma Rifle, Plasma Repeater, Spiker, automag, Silenced SMG, Brute Plasma Rifle, Covanent Carbine, Sentinel Beam.
* Grenade Spree: Get 5 kills with grenades.
* Pull The Pin: Get 10 kills with grenades.
* Cowbell: Get 15 kills with grenades.
Frag, Sticky, Spike.
* Launcher Spree: get 5 kills with a grenade launcher.
* Up 'N Atom: Get 10 kills with a grenade launcher.
* Johnny K.: Get 15 kills with a grenade launcher.
Brute Shot, Grenade Launcher, Plasma Launcher, Concussion Rifle.
* Rocket Spree: Get 5 kills with a rocket launcher.
* Mr. Torque: Get 10 kills with a rocket launcher.
* Splosion Man: Get 15 kills with a rocket launcher.
Rocket Launcher, Fuel Rod Cannon.
* Shotgun Spree: Get 5 kills with a shotgun.
* Open Season: Get 10 kills with a shotgun.
* Buck Wild: Get 15 Kills with a shotgun.
* Sniper Spree: Get 5 kills with a sniper.
* Sharpshooter: Get 10 kills with a sniper.
* Be The Bullet: Get 15 kills with a sniper.
Sniper Rifle, Beam Rifle, Focus Rifle.
Lazer Spree: Get 5 kills with a Spartan Lazer.
Red Menace: Get 10 kills with a Spartan Lazer.
Sunburst: Get 15 kills with a Spartan Lazer.
Sword Spree: Get 5 kills with an Energy Sword.
Slice 'n Dice: Get 10 kills with an Energy Sword.
Cutting Crew: Get 15 kills with an Energy Sword.
* Hammer Spree: Get 5 kills with a hammer.
* Dream Crusher: Get 10 kills with a hammer.
* Wrecking Crew: Get 15 kills with a hammer.
Gravity Hammer, Golf Club.
Needle Spree: Get 5 kills using needles.
Pink And Deadly: Get 10 kills using needles.
Fear The Pink Mist: 15 kills using needles.
Needler, Needle Rifle.
*Sticky Spree: Stick 5 opponents.
*Sticky Fingers: Stick 10 opponents.
*Corrected: Stick 15 opponents.
Splatter Spree: Splatter 5 enemies with a vehicle.
Vehicular Manslaughter: Splatter 10 enemies with a vehicle.
Sunday Driver: Splatter 15 enemies with a vehicle.
Assist Spree: Assist in killing an opponent 5 times.
Sidekick: Assist in killing an opponent 10 times.
Second Gunman: Assist in killing an opponent 15 times.
Bodyguard: obtain 5 Protector medals in a row.
Wingman: Obtain 10 Protector medals in a row.
Third Wheel: 15 Protector medals in a row.
Spawn Spree: Spawn 5 teammates into a game.
Copilot: Spawn 10 teammates into a game.
BFF: Spawn 15 teammates into a game.
Infetcion Spree: Infect 5 players.
Mmmm Brains: Infect 10 players.
Thriller: Infect 15 players.
Zombie Killing Spree: Kill 5 zombies.
Hell's Janitor: Kill 10 zombies.
Hell's Jerome: Kill 15 Zombies.
Juggernaut Spree: Get 5 kills as Juggernaut.
Immovable Object: Get 10 kills as Juggernaut.
Unstoppable Force: Get 15 kills as Juggernaut.
EMP Blast: Use an EMP blast to instantly remove an enemy's shield before killing them.
Needle Supercombine: Kill an opponent using a needle Supercombine explosion.
Incineration: Burn an enemy using fire.
Laser Kill: Kill an enemy using a Spartan Laser.
Sniper kill: Kill an enemy with a sniper headshot.
Headshot: Kill an enemy with a headshot.
Headcase: Kill a sprinting enemy with a headshot.
Extermination: Wipe out an enemy team with at least an Overkill.
Perfection: Win a Slayer game with the MVP medal without dying.
MVP: Complete a slayer game with the most kills and least deaths.
Steaktacular: Win a matchmade game by at least 20 kills.
Pummel: Melee kill an enemy.
Beat down: Melee kill an enemy from behind.
Assassination: Perform a successful assassination animation.
Yoink!: Kill an enemy while they are being assassinated.
Avenger: Kill an opponent who recently killed your teammate.
Bulltrue: Kill an opponent who is in the act of a fatal melee lunge.
Environmentalist: Obtain a kill using environmental weapons.
First Strike: Earn the first kill of a match.
Grenade Stick: Stick an enemy.
Splatter: Run over and kill an enemy.
Death By The Grave: Kill an enemy postmortem.
Killjoy: End an opponent's spree. Any Spree.
Protector: Save a teammate by killing their attacker.
Close Call: Survive a firefight with low health.
Hijack: Steal an enemy occupied ground vehicle.
Skyjack: Steal an enemy occupied aircraft.
Reload This: Kill an opponent who is reloading
Revenge: Kill the enemy responsible for your last death.
Showstopper: Stop an assassination by killing the assassinating opponent.
Rejected: Survive massive damage by countering the attack. (Gravity hammer to a rocket, etc.)
Assist: Assist a player in achieving a kill.
Wheelman: Be driving the vehicle when a passenger makes a kill.
1st Place: Win a race.
Last Man Standing: Be the last survivor in a game of Infection.
Objective Kill: Kill while holding the objective.
Courrier Kill: Kill an enemy courrier.
Objective Delivered: Deliver the objective to its destination.
Objective return: Return the enemy's objective.
Skullamanjaro: Deliver 10 skulls in Headhunter.
I'm not doing Promethean weapons or styles, because the Prometheans are flat out gay, they suck donkey -yoink!-, if you at all liked them, you may as well suck donkey -yoink!- too, my opinion's not gonna change. Prometheans can -yoink!- off.
I'm also not doing anything new in Halo Infinite, since I wouldn't know. By the way, kudos if you read it all.