Given that the Harrier is:
the attack aircraft in its primary role
close a2a capable
SEAD/DEAD capable
still the iron bomber
fast and subsonic
I can conclude, that the Su-25T is the closest aircraft according to these points. Removed SEAD/DEAD, Su-25 is next. No other attack plane (in its primary role) combines the speed and wide armament nomenclature. But if we are talking about the vibe, Su-25T has a different one. And is Su-25 is another different thing.