Here are a couple ideas:
Clan streaks in 4s or 6s: If you can put a lot of streaks on a Stormcrow, TImberwolf, Maddog, etc, that could help you out. Streaks are high damage but they spread it everywhere. For KMDD, not to big of an issue as long as you did the most damage to the target. Extra effective against lights because they have less health, both for the purpose of killing and getting the biggest proportion of damage dealt.
IS Pulse Laser boats: I used the Banshee. 3 LPLs + some MLs or MPLs. I like the Inner Sphere mechs for this kind of build (for less time on target), particularly the Banshee because of its high mounts, shield arms, and good speed. Generally a solid build. Also try on Stalkers, Thunderbolts, Battlemasters, Awesomes, etc.
LRM boats: self explanatory. Lots of potential points because you can hit lots of targets for lots of damage without having to run around the map as much. More dependant on teammates though and might not be as consistent as a direct-fire mech.
DPS Ballistic Builds: Dire Wolf, Ilya Muromets, Jagermech, Mauler, King Crab, etc. Lots of potential damage but also a lot of required time on target.
Pinpoint Front loaded build: AC40, Dual Gauss, PPCs. Tricky to do but if you have good aim and good awareness, you can kill mechs fast (specifically Inner Sphere XL engines). I wouldn't personally recommend it for this challenge.
SRM brawlers: Pair with AC20 (ie. Atlas brawlers), or medium lasers. Gotta get pretty close so pick a durable mech and be extra careful with positioning.
Edited by Takashi Uchida, 17 January 2016 - 04:06 PM.