MJOLNIR has two modes of operation. The first is a long distance, variable-output particle cannon that's capable of warship-vaporizing particle beam blasts.
The second mode is a massive energy sword whose blade is around 735 feet (224m) long and 46 feet (14m) wide. This is roughly half the size of the largest version of Morglay. While in sword mode, MJOLNIR can also be thrown and retrieved for razor-edged cuts that can cleave entire warships in half, from an impressive range.
Blue Beetle also uses this huge weapon in close quarters melee fighting, as was demonstrated against the A-10Dolls in ME0 - Ch57.