There is more than one artist with this name:
1) Under Pressure Late 80's NYHC. Under Pressure had a heavy sound in the vein of bands like Outburst, Breakdown, Raw Deal etc, with a bit of a patriotic slant in the lyric department. The band recorded a demo in 1988 and appeared on the New Breed comp.
2) Under Pressure from Winnipeg, Canada play hardcore punk influenced by Poison Idea, Motorhead, Black Flag, with hints of NYHC here and there. 3) Under Pressure is an underground hiphop crew formed in 2006 in Athens, Greece. Their lyrics are mainly of social or political concern.