That remind me of another mistake I made that I tried to block from my memory.  Not bent pins but I once forgot to apply the washers when installing the heatsink on the CPU.  Worked fine for a few years then a friend gave me a cpu that was an very minor upgrade from the one inside but it was free so why not and I went to remove the heat sink.  The skews had gone through the motherboards holes.  Nothing I did could get those damm things out.  I ended up getting so frustrated that I align a small skew driver under them and then banged it with a hammer and kept banging harder and harder till I finally did get them out.  That motherboard never worked again.  That free upgraded on a old computer ended up costing me over $100 for the replacement motherboard.  

In the early days of learning to build PCs I had trouble figuring out how the liquid cooler was meant to go when I first decided to use them and actually fit it where the back fan would be instead of on the top of the case which had the grill for such coolers to be fitted. I used to go overkill on the PSUs as well meaning more money was spent than should have been.

My second PC was the first I built personally. After assembling it, I turn it on, a green LED on the mobo lights up, all the fans and the HDDs start turning for a second or two, then everything turns off. I try both reset and power button, nothing happens, I turn off and on again the PSU, again everything turns on a few seconds, then off again, after a few tries, I give up andtake the PC to a store's technicians. A few tens euros and they give it back to me perfectly working: I hadn't connected the case front panel to the mobo.

About 17 years ago a friend of mine blew up a new AMD Athlon chip because he put it in the motherboard without a heatsink on and it blew up.
Most chips these days are tougher than that though.
Personally i had to take an AMD build to a computer shop around the same time because i had put the AMD chip into the motherboard the wrong way, this chip didn't have a few pins missing in the corner to guide you on how to insert it.Luckily no harm done to the hardware only to my ego as the tech there fixed it within 5 seconds.

Forced my cpu out forgetting their was a lever. Somehow the pins only bent and I bent them back carefully

I was going to say you were unlucky as even if you completely removed a cooler the GPU will turn itself off long before it damages itself.

Then realised that GPU came out in 2003. Unlucky.

Yeah sucks though bearing in mind these were the days when high end GPU's were relatively 'cheap'. Was under £130 iirc. Can't remember what GPU I replaced it with but it was inexpensive.

I would die a little inside if this happened to a modern higher end GPU though lol. Ain't messing around third party coolers on £500+ GPU's.

Had an AMD K6-2 300mhz back in the day under liquid nitrogen doing some extreme overclocking... Case was naturally laying on it's side with the guts exposed... Knocked my cup of hot coffee from the desk which landed inside the machine.

Lots of paper towel later... It still fired up.

Unfortunately electromigration had set in by that point anyway which meant the chip couldn't clock faster than 133mhz without a blue screen.

At somepoint during 2021 i need to buy a bigger SSD 2 TB, 4 TB Harddrive that goes into my tower, Better graphics card i have a 970 at the moment and better power supply and cooling fan.

In mid 2000s I got obsessed with silencing my PC and wasted quite a lot of money with unsatisfactory results.

Around that time I fried my AthlonXP 1900+ by installing the cooler wrongly.

The last mistake was this year when I connected an old LED light to my PSU, I don't know what I did wrong but my motherboard fried, luckily everything else survived.