''I thought you knew that pity was a four-letter word,'' Lajon Witherspoon barks near the start of Sevendust's sixth studio disc, Alpha. ''Now I feel the need to make you suffer,'' he adds a few minutes later. At least he's honest. The band mercilessly assaults listeners on songs like ''Aggression'' and ''Confessions of Hatred,'' burying every potential hook under a barrage of enraged howls and pummeling guitars. Witherspoon's singing voice is far more expressive than his screams; too bad he uses it so infrequently here.