Well that's the thing... I flashed the image that was provided for my build/version, still nothing.... and now I can't get it to even turn the screen on at any moment, I cannot flash another image because I can't get into fastboot (I did it on slot a btw, slot b is -or should- still be untouched)... I have downloaded the stock fastboot, but whenever I try to flash it with MiFlash it requests authentication for some reason (I have bootloader unlocked).... so I don't know what to do.
No, it was not that, the issue was on the image I was trying to flash in order to solve the issue. It was asking me for some account login on MiFlash, but that was because I was using the official from the Mi official site. After trying to flash using MiFlash again on EDL mode using another image it worked ok... good thing, however I lost all my data
Anyways, small price to pay instead of having to pay someone or having to buy a new phone.