Question Is my CPU dead ?

[kraken43]

So the PC turns on, the motherboard LEDs light up , the graphics card lights up and spins for 3 sec and turns off but the led stays on

I get no display and keyboard and mouse doesn't work

So things I have already tried
1)Reseating a single ram on each slot and trying other Rams on each slots
2)tried resetting the cmos
3)replaced the graphics card with my older graphics card which is in working condition ,still got the same result (so my graphics card is fine )
4)tried a different psu from a different computer which had a working psu ,still the same result
(My PC had a 750w psu and the one I tired was a 550w psu)
5)got a new motherboard and plugged everything properly and still the same result

One of the things I noticed while checking my current motherboard for anything damaged ,
I found 1 pin in the motherboard socket bent ,
So I fixed it and replugged everything again , still the same result

So since i have replaced and tried on different hardware , the only thing I haven't replaced is the CPU

So is my CPU the problem ?
Is my CPU dead?
Should I try other things ?

So my specs are
CPU - i5 6600k (was overclocked to 4.5ghz)
Motherboard- Asus z170 pro gaming
New motherboard ( this was just for testing ) - gigabyte ga-h110m-s2
Gpu - gtx 1070
My older gpu - gtx 960(used for testing)
Psu - Corsair cx750 750w
Psu used for testing - Corsair 550w
Ram - gskill trident z 16gb 8x2
2 tb hard disk and an SSD

Sorry for bad English not my first language and sorry for the long post
Please help

 

[Quanticriver]

Given that you have checked most options - it would leave the cpu...
that bent pin doesn't seem good- if you inspect the back of your cpu, is there anything you can see?

also try breadboarding the pc to see if that works, maybe your casing is making it shortcircuit