All Achievement List for Ion Fury
This guide is written under the assumption that you have an understanding of Ion Fury enough to play the game to a satisfactory degree. You should be able to obtain all of the achievements herein in a single play through.
Ion Fury - Complete the game on Maximum Fury difficulty
Your goal is to see this unlocked at the end of the guide. Let's get started!
Progression / Unmissable Unlocks
Story, Scenarios and Bosses
Dedicated - Complete the game on Maximum Fury difficulty
Self-explanatory, the difficulty option is immediately available. It's first on the list because it's what you need to know the most, play on this difficulty to maximize your time. This game is long, but not as brutal as the tagline says. Ignore the warning, and also ignore the adage of retro shooters that you need to learn enemy placement to be effective. Always assume the room ahead is stuffed with enemies, and always scour for secrets to have enough ammo to deal with them.
The following cannot be missed
Shaken, Not Stirred - Step out of the bar
Altar of Sacrifice - Survive the Onslaught
The Future of Law Enforcement - Demolish Heskel's oversized security droid
Hunter, Killed - Defeat the Revenant 8991-PX
Express Elevator - Survive Heskel's horribly overdesigned trap
Mech Warrior - Clear the lab of Warmechs
Brutalized - Separate the Twins
Capital Defense - Defeat Dr. Heskel
Seeing Cyber Red
Firepower Matters - Collect all weapons
Simply pick up every weapon at least once. The last weapon you should have to obtain is the chain-gun, earned after the mech boss fight, as every other weapon is found while secret hunting.
Demanufacture - Decapitate 100 enemies
Aim for the head until you see red, and know that it be dead.
Cranium d'Or - Kick 20 severed heads
Will come naturally as you sift through the carnage you leave after each battle.
Arachnophobia - Kill 20 spiders with the Electrifryer
Hit them with MB1, and they'll do a quick spin before bursting. Tip- Press [Q] to quickly swap to the Electrifryer, and again to your previous weapon.
Demolition Turkey - Get 3 Strikes (3 or more killed) with Bowling Bombs
Will pop quickly, sooner during the arena battle in episode one's final map, especially with the Bowling Bomb power-up. Heskel's House of Horrors has a bowling alley that will hand this achievement to you on a silver platter.
Overkill - Kill 30 flying enemies with explosives
Don't waste Clusterpucks, and if you can somehow lob a Bowling Bomb at them, more power to you. Otherwise, you're weapon of choice is the grenade launcher. Either press the alt-fire key on the shotgun, or  and aim carefully.
Searching every nook and cranny...
A Secret Place - Find 50 of ♥♥♥'s secret stashes
If you're aiming for 100%, scour every inch of the map for secret doors, destroyable walls or interactable switches... or use Pagb666's secret hunting guide.
Bad Mojo - Stomp 20 cockroaches
You'll most likely earn this without knowing it. The sound effect for squishing them is rather silent, and they infest most vents, which you'll be using quite often to navigate levels or towards secrets.
Cowabunga! - Eat 30 slices of pizza
You'll find slices of pizza everywhere, just scarf it down as you go.
Quenched Thirst - Drink 20 cans of soda
You'll find soda lying around, and most vending machines will give you five sodas before running out.
Mega-Secrets and More!
These require you to locate specific events within secrets, often mega-secrets, to obtain. I'm not 100% if these are correct, as I discovered them prior to the 1.02 patch that unlocked all of them.
Peanuts and Cracker Jacks
The secret level Grand Slam. use Pagb666's Guide to enter. You obtain the card before the fight with the Revenant 8991-PX, and then enter after taking the elevator down.
Found in the first level, near the giant MDK sign. Follow Pagb666's video starting here to get there.
All Doors Are Locked
Found by activating switches, a reference to Silent Hill 4: The Room.
Resident Evil reference, found after returning to Hazard Disposal.
Found in the D.C. Meltdown super secret.
Diddle In the Middle
I'm 98.2% sure it's this secret, which reveals the code for the piano.
Total and Complete Meltdown
Mega-Secret referencing Chernobyl.
The Owls Are Not What They Seem
I believe it refers to this non-secret. It requires you to enter a specific room that's a Twin Peaks reference.
Files indicate it's a 100% achievement. Earned most likely through discovering every countable secret, mega-secret, the secret level and killing every enemy.