Tag the marker to launch the Kingpin's Seoul debut. Follow Hollywood's directions to a local hotspot, and gun down the local hotheads. Loot crates may also be available.
Your SMGs do a surprising amount of damage (at least on Level 1), but you need to be close. Don't worry too much about headshots- even firing from the hip you can down many of these early enemies with even a few glancing shots. As will be the pattern, the party's over when you down the commander.
The next hot spot is a shopping center, where you will kill an awful lot of people. The Gun Machine power makes things easier- but keep in mind that only enemies caught in the initial blast are affected by the debuffs.
The commander here uses groudpounding area attacks- keep mobile and let him just charge straight into your bullets.
The last hot spot is a rooftop party. No need to leap your way up though- you can just follow your marker to the front door.
This party gets very crowded, very fast. When using Kingpin's Dance Party ability, which compels enemies to dance (shades of Captain Eo, there), prioritize the healing generators as targets- they'll make everyone else that much easier to dispose of. Do try to avoid tagging civilians, who turn into glowing red fiends when aroused.
When the last of the actual bad guys falls, the mission is complete, and Kingpin is added to your roster.