I got into many red LED situations, I was able to come out of it everytime by using the procedure I posted above (that post was from pure experience I had).
red led bootloop unbrick procedure
1. plug phone into USB cable connected to computer
2. wait for it to go into charge animation
3. unplug, then press power button to boot, immediately press vol up + vol down.
4. hopefully you booted into bootloader mode (rinse and repeat steps 1~4 if you can't get to this point)
5. chose recovery (if your recovery is corrupted, repeat steps 1~4 and do fastboot flash recovery cwmxxx.img)
6. from recovery choose restart system
if you can't get to step 2, because N4 has a bug with battery capacity, plug your phone into AC charge and let it charge for a few mins. then restart from step 1...
red led bootloop unbrick procedure
1. plug phone into USB cable connected to computer
2. wait for it to go into charge animation
3. unplug, then press power button to boot, immediately press vol up + vol down.
4. hopefully you booted into bootloader mode (rinse and repeat steps 1~4 if you can't get to this point)
5. chose recovery (if your recovery is corrupted, repeat steps 1~4 and do fastboot flash recovery cwmxxx.img)
6. from recovery choose restart system
if you can't get to step 2, because N4 has a bug with battery capacity, plug your phone into AC charge and let it charge for a few mins. then restart from step 1...