What were your favorite steam games to do all achievements in?

For me Kingdom Rush :)
I still replay it from time to time.

Gems of War
Quake Champions

Eh, I've done it a few times now. Dunno if I have a favourite "100% completion " game.

Frozen Synapse.

There's an achievement "He Has a Better Beard Than You, Though" for defeating a specific user named Bin (one of the devs I think). Usually I hate those kinds of achievements. I was playing it in 2015 and the multiplayer was already dying. That's exactly the reason why no game should have such achievements. I couldn't hate this game though, it was simply awesome so I continued playing without hoping for 100%. But then suddenly this Bin guy showed up and accepted my challenge. The match continued for a few days (it's an asynchronous multiplayer) and I remember at some point I suddenly saw that I could really win it. Maybe the guy was out of practice or maybe he was just trying to help people get the achievement. So I won and that was it.

Honorable mention: GemCraft - Chasing Shadows. Took me a while 270 h :)

I think Goat Simulator was the most fun one. There are so many achievements for doing the most random crap and collecting them all was a blast.

Beat Saber probably. I enjoy achievement hunting, but that’s the only game I’ve put in an extra 100+ hours once all achievements have been done! (I’ve played most hours on my oculus version, was a lot better wireless latency wise at expert+ levels).

The only one that was neither overly simple nor required tedious grinding was Dirt 4 - some simple ones, some not so simple, an achievement for every stage in career. Overly it was fun to play the game and for a regular gamer - possible to get all achievements.

https://www.trueachievements.com/a235334/mondays-be-like-achievement - this was funny. I couldn't understand why I can't seem to get this achievement. Turns out you can get it if you crash your car on monday...

PS. I do remember now that there was some grind though - there are some multiplayer specific achievements (that should be abolished by law, because games inevitably die off...). I had to find people in discussions and they had created group chat and got together at times to play to get those achievements. I still stand by that this game was my favorite 100% game - but this was tedious. First Dirt Rally game is even more horrific - it has achievement that only people in early access got. so people getting game after can't physically get it.... Well that's what I call an asshole move.

Loved to get (the not-challenge) achievements in Dishonored, one of my favourites. Half Life 2 comes to my mind as well, with good mix of story, collectible and silly achievements.

Train Valley 2

Mad Max https://store.steampowered.com/app/234140/Mad_Max/
Dex https://store.steampowered.com/app/269650/Dex/
Wolfenstein:The new order https://store.steampowered.com/app/201810/Wolfenstein_The_New_Order/
Life is Strange https://store.steampowered.com/app/319630/Life_is_Strange__Episode_1/
The Walking Dead https://store.steampowered.com/app/207610/The_Walking_Dead/
The Walking Dead Season 2 https://store.steampowered.com/app/261030/The_Walking_Dead_Season_Two/

"A World of Keflings" and "A Kingdom for Keflings" on Xbox with my dad were a blast to 100%. We LOVED playing that. We still play it again every couple of years or so. I wish there was a new Keflings game on the same style.

Also, "Mirror" and "Crush Crush" on Steam were a pleasure to 100% ( ͡° ͜ʖ ͡°)

And Helltaker too! I love that game way too much.

I've not got 100% in many games, but Horace was by far the most enjoyable! It's such an awesome game :D

UnEpic - https://store.steampowered.com/app/233980/UnEpic 😊

Jazzpunk

I first played Psychonauts on PS2 when I was eleven or twelve, and I remember thinking 'I can't imagine anyone ever collecting all those figments!' Then I replayed it as an adult on Steam and took on the challenge. Better equipped and with more skill, I took a lot of joy in finally completing that challenge.

I feel similarly about Okami. When I replayed it as an adult I realized there were a lot of things - even whole side missions and areas - that I completely missed as a child. Doing them now and finding all of the beads was really satisfying.

So I think that's the key - rediscovering the true depth of games I loved as a kid and seeing how far I've come.

I was obsessed with Enter the gungeon. And after 150h investment 100% was done.

Probably The Binding of Isaac

I guess Civilization V, especially for the super hard ones for the scenarios.

Train Simulator! ... Just joking, I have only 10 percent of those 1280 achievements even though I played the game for 330 hours. :-)

What I really enjoyed recently was Lara Croft GO - the achievements are pretty easy there, but playing the game was very enjoyable for me, I hope they will make a sequel.

Binding of Isaac, but that one I'm still trying to complete haha at least is really fun still

Dicey Dungeons (not the most particularly unique chieves but loved the game/completing it)!
Redout: Enhanced Edition is another favourite and the final-final race had a tricky level, was definitely satisfying getting first.
Jazzpunk had some fun ones, much like the game.

Definitely
https://store.steampowered.com/app/372540/The_Lost_Mythologies/

Stardew Valley
Terraria