I'll add that I managed to do it only once and had only one spare life when I beat the Dark Queen.

I got ridiculously good at COD4 multiplayer back in the day. In one TDM game I got 52 kills and a 32 kill streak. I'm also fairly good at the Sonic Adventure games, scoring pretty high on some of the leaderboards.

There are quite a few games that I can't seem to master no matter how many times I play them. I've been playing Resident Evil 3 since I was 4 and I still can't complete it on hard mode today.

Ratchet and Clank 3 beat it over 10 times and just roll through that stuff now even the time trails on Quark levels

Metal Gear Solid Peace Walker. I have replayed all the Main Ops and Extra Ops and S ranked them all with my best friend to get ALL the Design Specs for the weapons and items. I have them all, but I still haven't managed to get the usages of all weapons to Level 3. I was a bit close to get the FOXHOUND rank, but I made a mistake halfway, and decided not to keep trying to get it. Still, I got all of the mechs, I found all of the alternate parts for Zeke and I got all of the memory boards, which makes him a beast. And the Monster Hunter missions... damn them. Tigrex specifically. He's even more difficult to beat than Gear Rex.

My friend and I spent many days doing all the mech Extra Ops, whether it was to capture mechs by S ranking the mission, or just blowing the hell out of everyone with RPG's, the Raligun while one of us charged it with the Dynamo, CO-OP Thunder, or any other hilarious way to take care of them. We have tried every possible mission in every outfit:

Naked with camo pants for that extra challenge
Neo Moss camo for mech battles
Sneaking Suit was my favorite of them all. It was my default outfit. Used it almost all the time for mech captures.
Battle Armor for those AI mech battles. Chrysalis Custom was a pain in the ass.
Tuxedo, just for laughs.
Swim Trunks for more laughs.

I have also spent a lot of time recruiting S ranked soldiers to use on the missions and Versus Ops. Thanks to it, I know a lot of dialogue lines from memory, especially Big Boss' raspy "You're fired!". I knew who was S ranked just from fighting them. I have even found an exploit to keep doing recruitment for a while. I got obsessed finding a soldier with a certain face in S rank, but it was IMPOSSIBLE! Not even my other PSN friends had him in S rank.

If you have him in S rank or near S rank, please contact me

While I suck at every other multiplayer, I beasted at Versus Ops. Sure, it's like a kid's version of MGO, but it was damn fun and I won a lot of times there. Sure, there was a lot more people who was better than me, but I was also good, and that was enough for me. I always used the sneaking suit because it was tactically superior to the loud BDU's.

In the end, I platinumed the game before I really had fun with it. Once, I deleted a 200 hours saved game while on a blind rage. I repeated the game and I currently have 300-400 hours. So I could say with security I have mastered this game.

Resident Evil 4 on GameCube. Not sure how many times I played through it but for a game that's fairly hard
by the end of it I was owning that shit....

Quake 3
CS 1.6
Super Smash Bros. Melee

Also my most-played games in general.

I can complete Half-Life on hard mode without taking damage.
I have gotten Golden God+ in Super Meat Boy... 6 times.
I had a 1.6 K/D ratio in Resistance 2... without abusing the Wraith.

I used to beat Mike Tyson's Punch Out, Shadow of the Ninja, and Double Dragon II a couple times a day. I played with my hands behind my back for a tiny bit of extra difficulty.

I have three save files for Final Fantasy Tactics with every character/weapon/item and all characters with all jobs maxed. Getting all hidden items from Deep Dungeon is quite a challenge.

Resident Evil 4 Wii Edition. I had to unlock every weapon. Those stupid side missions were horrible. So I kept replaying everything. After 8 months of playing the game every free time I had. I remembered all the positions of the zombies. And can eliminate them really fast. I know one time in the house as they come in. I finished them before they even moved. I remember the full sequence and threw grandes or shot them as them spawned out the doors and windows.

Quake III, Unreal Tournament and CS 1.6 were the only reasons I even bothered with PC gaming back in the day..