Green has the widest array of creatures to draw upon, ranging across all power levels, and generally is able to dominate the battlefield with many creatures in play at once
Also consider Nameless One
Although it has since proven to be much quicker to defeat than that for appropriately leveled and equipped characters, it's still a memorable boss, especially given the initial hype surrounding it
Plus, you can open all sorts of cards with Booster Fun treatments, such as cards with the showcase magnified treatment, each depicting a story spotlight moment from working on the case
It includes 6 Foil Borderless Scene Cards, 6 Art Cards, 3 Play Boosters, and 1 Display Easel
Settle the Wreckage is a vital card for U/W Approach out of the gate, as it replaces the previous cheap removal that has rotated out