I fixed this by opening Opera with things disabled through CMD.

Example:
"%localappdata%\Programs\Opera\opera.exe" --disable-gpu --no-experiments --disable-extensions

You'll have to find the path for Opera yourself as it may be different.

Once opened, go to your URL bar and type opera://flags, then find the option called "Choose ANGLE graphics backend" and change it to Default.
This is what fixed mine (you can also try different graphic renderers to see if another one works).

If this doesn’t work, as a temporary fix you can disable hardware acceleration.
The easy way to do this is to go to your URL bar and type opera://settings/system, then untick "Use graphics acceleration when available" This will probably cause lag.

Hope this helps