My external monitor is dark at full brightness

(MacBook Pro 16 inch 2019) I am using an external monitor and ever since I accidentally deleted my OS and installed a new Mac OS (Big Sur 11.6.1), my monitor is very dim and dark even on full brightness (both Mac and monitor settings).

I thought this was an issue with my monitor, but when I try using windows with Bootcamp, the monitor becomes as bright as I expect it to be, so I am assuming there is something wrong with my Mac itself. Also, not sure if this will help, but when I am shutting down my Mac and only my desktop background remains before turning off, the brightness becomes bright for a slight moment (hope this makes sense).

I tried pretty much everything I knew about, including recalibrating the colours. Anyone with an idea on how to fix this?