Cause it has for me. I'm playing Trigger Happy Havoc on Gamepass, and after *spoilers ahead*

Sure enough...

So, have achievements ever spoiled a game for you?

I would say the online trophies for pole positions and 92 victories in GT Sport are a big reason why races are often a mess. People keep tanking their ratings to get these trophies and use dirty tactics to get the victory. Then of course they are addicted to the easy victories while sandbagging and continue. Instead of trophies for pole positions and victories, PD should have added trophies for clean races and maintaining high SR rating.

I don't bother with trophies and achievements anymore. They pop up, I ignore. Last gen I did sometimes chase trophies but it never improved the game. X kills with this weapon... just play the way you want to. Games have enough to do lists build in already. Going after a trophy basically means the game is lacking fun, looking for something to do instead.

I don't think they ever spoiled any plot points for me, can't remember. What I do find a bit spoilery is indeed those journals and ability pages you fill in while playing. You can already see what's coming and how much is left.

No because I do not decide to plat or 100% a game until after I beat it, and see if I am ready to move on or not.

Never really got the appeal of achievements.

There are a couple of games where after I have completed them I might look at some form of achievements to see if I missed anything, as I haven't owned a PS or XB console usually this is in-game achievements or something more akin to stats pages like in GTA.

The account based achievements I have access to are Steam, Origin & Uplay (the latter two against my wishes) & I mostly ignore them or turn them off. I don't mind certain kinds for example "kill [x] number of enemies using [interesting method]" like Mass Effect 3 where it counts letterboxes, but TBH this would still be better suited to just being tracked in a game stats page that you can view when you want rather than having to pop up a box when you pass certain milestones.

The only games I have played with genuinely interesting achievements in have been The Stanley Parable & Breathedge, and that's pretty much because they take the piss out of the achievement system as a whole.

I feel like my question has been misinterpreted. I wasn't talking about achievements ruining a game for you. I meant achievements revealing part of the story in a game.

Ah I see, as in spoiled the plot/revealed something before you get to it.

Well as I ignore them they couldn't, but if plot elements are put into acheivements that's poor design choice.

No, spoilers don't bother me. Sometimes I look for them. Tho sometimes very rarely I like being surprised. No More Heroes III and Nier Replicant had a couple that shocked me and glad I was surprised. That's super rare.

I've never had a feeling that they ruined something for me, because I don't look at them ahead of time.
I do agree that they sometimes give things away though. For example, there is a bunch of talk about the "revive three teammates in one life" achievement in Halo Infinite lately. It has given away the fact that a new game mode is coming at some point, as it is impossible to do what it says with current game modes.

I don't look at them ahead of time, but sometimes they can give future plot points away as they're earned. See the spoiler text in OP as an example. 

I feel like they have but I can't think of a specific one.

They do often take away from the gravity of certain moments, though. Like your best friend might die in some super sad way and while you're still drinking in the moment, you see "End of an Era +50pts" pop up on the screen.

I love achievements, though. I don't really go too far out of my way to get them but they make me feel like I've accomplished something.