White Screen of Death on Bootup

I'm have this iMac that has some trouble. Heres the story: I found this old iMac amongst my brothers stuff, but it had a white screen on boot, I then booted into safe mode, and it went just fine. I reinstalled the entire OS X from Mavericks into Sierra, and I'm still having trouble booting. I keep getting white screen on boot, however Safe Mode boots just fine. I have already done:

First aid in disk utility.

Reinstalled OS X.

Reset NVRAM.

The iMac is a Late 2009 model, 3.06 GHz, 12GB Ram, 1.5TB HDD.

It was a clean reinstall from USB.

I was thinking that it might be the dedicated graphics card (Radeon 4670 HD) that is at fault, since it might use onboard graphics instead when you boot in Safe mode. Any help is greatly appreciated.