bystander :
Brightness levels might do this for some. For me it is latency, but everyone is different. These monitors today are extraordinarily bright out of the box. I use my monitor at 30% brightness.
It turns out it strobes the LEDs to adjust brightness. So if I turn brightness all the way up it doesn't bother me (except for being blindingly bright), but that is hardly a solution. So I'm returning it to amazon. Bummer. I think the real solution is not buying a monitor I have never looked at before.
here is a quote from https://pcmonitors.info/reviews/aoc-g2460pqu/
"The AOC g2460Pqu uses PWM (Pulse Width Modulation) to dim the backlight below 100%. That means that the backlight switches on and off extremely rapidly to produce lower bright nesses. A minority of users are sensitive to this flickering and can suffer from visual discomfort (headaches etc.) when viewing a monitor that uses PWM. Aside from the BenQ XL2420TE, which is expensive and restricted to certain regions currently, all modern 120Hz+ LCDs use PWM and it isn’t something most users have to worry about. The video below shows the existence of PWM on this monitor as captured by a sensitive camera – nobody detects such a pronounced strobing, that’s just to demonstrate its existence. Note the lack of strobing in the video at 100% brightness, where PWM is not used as the backlight is not being dimmed."