Demolisher is a vehicle in Battletech.
The Demolisher is one of the most dangerous vehicles to encounter, and can easily punish an unaware commander. With an initiative of 1, it's one the last units to move in a round, but with twin AC/20's, it can easily blast a hole in heavy 'Mechs, or even bring down a light 'Mech in 1 salvo. Eliminating it quickly is imperative, and can easily be done by stomping on it with a big enough mech at the beginning of a round, without giving it a chance to fire. However, when its with maxed armor, only the biggest and strongest mechs can 1 stomp kill it, making it usually requiring a lot of concentrated firepower to take down.
The biggest problem of the Demolisher, other than its firepower, is its durability. When in good repair, the Front and Turret can each survive a pair of AC-20 hits before suffering internal damage, and the damage distribution system make it all but inevitable that hits will divert to the sides. The sides themselves are significantly weaker, but often require a precision shot to ensure destruction in one salvo. LRM barrages are only moderately effective, often running head first into the scatter shot problem.
And god help you if they're both in cover and have other units to act at spotters.