You’ll earn this achievement for completing any one of the three Mass Effect games on Insanity difficulty. Mass Effect 1 is by far the easiest of the three games, just make sure you change the difficulty to Insanity while you’re on the Normandy before you deploy to Eden Prime.
If you want to make things even easier, wait until you second playthrough before you attempt this. Waiting has a few significant advantages: first, you can simply skip a lot of stuff on the second playthrough, as all you really care about is beating the game, not scouring every planet and completing every assignment. Second, while enemies scale to Shepard’s level, much of your relative power comes from gear, and this does not scale with your level. You’ll generally start seeing some models of the best gear start appearing when Shepard’s level is in the early-to-mid 20s (Legendary Edition scaling), and while you might not get the highest-tier versions at this point, even a Colossus IX suit of armor is generally far superior to alternatives.
Some of the stats provided by this late-game equipment make the Insanity run much, much easier than even a start-from-scratch playthrough on Veteran difficulty. Damage Protection (provided by armor) reduces damage by a massive amount (generally in the range of 65-79% for Colossus Armor) while the cooldown bonuses provided by Savant Omni-Tools and Biotic Amps and by Medical Exoskeleton mods allows you to use abilities much quicker. Simply put, the potency of late-game gear is more than a match for enemy level and difficulty scaling. That’s not to say Insanity is all sunshine and roses - Husks and enemies that are fond of melee attacks (especially Krogan Warlords/Battlemasters) can potentially down Shepard in 2-3 hits, so some caution is needed.
Arguably the best build for Insanity is an Infiltrator with the Lift bonus talent, as they’ll have access to Colossus X Medium Armor (71 Damage Protection), most of the Engineer debuffs (Overload to boost damage and take down enemy shields, Sabotage to overheat enemy weapons, Damping to force enemy abilities to cooldown), while the aforementioned Lift is perhaps the best debilitative ability in the game, useful for thwarting charging Geth Destroyer and Krogan Warlords, and leaving enemies (including bosses!) helpless for extended periods of time. They might not have access to the heaviest armor or all the weapon types, but Sniper Rifles provide plenty of damage output in a pinch, and they’ll gain access to the Fitness tree, which will give them Immunity - the most potent defensive buff in the game. The Infiltrator is basically the best combination of DPS, tank, support and control you can get on one character… something of a “jack of all trades” that just so happens to be good to great at most of those roles.