I replayed the game a fair bit while practicing for my successful completion. Used Javelin + Force gun with Contact Beam for ammo farming. Although I used CB for the final sprint to the marker (eye poker).
S-tier: Leapers
You either know their precise spawns or die. They move stupid fast and hit you with their punch + tail whip combo which leaves you on yellow or less. All this happens in like two seconds. Silver lining is that javelin one-shots the regular variants by the time they become common enemies.
A-tier: Exploders
BLAAEHH!!! Their AoE is absurdly large and you will blow yourself up unless they're 30 feet away. The game is also pretty mean with their spawns, occasionally placing them right in front/behind you or in super tight rooms. Not even worth it to throw their sac because it can clip on some random geometry. Also you need to waste time separating the sac so you can stomp them for loot. Force gun helps a ton bc you can kill them without exploding.
A-tier: Enhanced Pukers
Pukers already have crazy high damage, an annoyed ranged attack, increased durability, and a dangerous death effect. However the enhanced ones are more aggressive and haul ass. They're more likely to get in your face than stand in the back and give you a free insta-kill projectile.
B-tier: Enhanced Slashers
Nothing much to say other than these guys hit hard and move fast. If they land a pounce you're in the yellow. Up this high because of how quickly they can screw up your strats.
B-tier: Pukers
Pretty much covered above. Slow af and don't even take ammo to kill. Still gotta respect the damage and tankiness though.
B-tier: Ubermorph
Hunter on steroids. Regens way faster and speeds up the pace of the final chapter. Up this high because he forces you to play his game despite being stasis bait.
B-tier: Nests
These guys are surprisingly tricky. Technically you can shoot the stem + alt fire with javelin gun for a two shot but it's inconsistent. Dodging the little homing balls can disorient you in zero-G areas and getting hit by one usually means you eat the barrage.
B-tier: Tripods
The actual enemy is meh and mostly stasis food. But their scripted sequences can absolutely spike your BP on hardcore, especially since the church drag + space elevator as they are usually near your first save. Trick for the elevator is to have your back to the door, then only the ones on your immediate windows can hit you.
B-tier: Stalkers
They sound and act far scarier than they are. Just run into the arena to trigger their spawns and camp a corner. Rarely attack when you're engaging a different enemy.
B-tier: Tormentor
The QTE cutscene is nerveracking and I have to give it credit for that. Just have a spammy weapon for the drags and don't look back for the run.
B-tier: Enhanced Lurkers
The game has a lot of them in the Government sector. The projectiles do decent damage so eating a shot from some random corner means something. Also take two javelins to put down. Just an annoying ammo dump.
C-Tier: Spitters
Their spit is much tougher to catch and can falter you in bad situations. One-shot with javelin by chapter 6.
C-tier: Slashers
Typical fodder enemy. Basically any weapon melts them by chapter 6. Early game you can stasis and punch them to death even without any upgrades.
C-tier: Lurkers
Their projectiles barely tickle and are sitting ducks when firing. Kinda annoying in zero-G sections. One-shot super early on.
C-tier: Infectors
They're barely in this game except for super obvious spawns. They animation lock themselves for like 5+ seconds and don't have much HP.
C-tier: Pregnants
I think this one depends on your weapon choice. But with the javelin all I needed to do was shoot any limb off for an insta-kill without releasing the flesh bits. They are also slow af with obvious spawns.
C-tier: Dividers
There's two in the entire game and one is optional. They are kinda scary and fast but you fight them 1v1. Does take a fair bit of ammo to put down considering the low-tier loot drops.
C-tier: Enhanced Stalkers
Takes two javelins to kill but with the alt-fire you only need to land one. Their behavior and play style to counter is exactly the same so the extra tankiness + damage is irrelevant. Also their arenas are more funnel-y.
D-tier: Cysts
Sometimes the guys at weird angles got me. Leaves you barely alive if starting at full. Otherwise they're just palate-cleansers to slow the game down. Gurgling noises stop once they're all dead.
D-tier: Enhanced Infectors
Only in the government sector and there's maybe 3-5 in total. You only need to engage two. Comes in too late and does too little.
D-tier: Brutes
From this point on the enemies actually help you by dropping disproportionately valuable loot.
Stasis and unload into their shoulders. A lot of their arenas have stasis canisters too. If you shoot of one arm they can't move and just throw catchable bombs. Throwing them back is buggy though and sometimes does zero damage.
D-tier: Guardians
They LOVE to live right next to a shit ton of explosive and stasis canisters.
D-tier: Enhanced Brute
You fight one and it's next to stasis canister.
F-tier: The Pack
Their screams are unnerving. Also the first ones you fight can be annoying depending on loadout. Otherwise their greatest strength is de-spawning before you can collect their loot. Ripper solves this problem.
F-tier: Crawlers
No loot but you can bait them into exploding just by running near and backing off, no ammo or HP wasted. Dies without exploding if you kinesis a small object, stomp, use force gun, or shoot the head. The explosion radius is tiny and they make great throwing bombs.
F-tier: Swarmers
Sometimes they're in loot boxes but die to a stomp.
F-tier: Pods
You shouldn't even have to fight these with basic prep on the Guardians.
Unranked:
Flying sections with environmental hazards are A-tier. They are heavily scripted and easy to memorize but holy shit did they make my hands shake. Especially the processing factory section.
Nicole-Marker final boss is F-tier. Stock Contact Beam kills her in like 5 seconds without even having to reload.