Need some help removing a kitchen sink drain
Tap (don't overdo it and break the "ears") with a hammer and nail or hammer and punch against the projecting "ears"  - and do as many of them as you can easily reach, rather than only tapping on the most accessible one (at least until the thing starts to move.)

Scribe a line before you start that goes across both parts so you can detect even a small movement. The shock of tapping may start to move things where grabbing with pliers won't budge it.

If no joy, add heat - use a serious heat gun if you have one, or a torch VERY carefully and pretty much so far out that the flame isn't directly contacting the sink parts, at least at first.