Director Krennic is a Trooper and Guardian focused Commander that offers powerful damage augmentation for figures of those traits using power tokens. These means he plays especially well with elite Death Troopers, as well as figures like Admiral Thrawn. Agent Kallus and Iden Versio also work great with Krennic thanks to their built in power token generating abilities, though with Kallus you'll have to choose which figure gets access to Advanced Com Systems which can make it a bit harder to use Kallus's ability. It might even be worth considering Temporary Alliance for a Clawdite figure, which in IACP no longer roll dice to determine the number of power tokens doled out by the Senator form, instead being just based on the number of dice (2 for the regular, 3 for the elite).
Of course Krennic brings his own supply of power tokens to the table through his Advanced Weapons Research ability and his unique command card. Make sure to bring Rule by Fear so you can maximize your chances of drawing Krennic's card before round 1.
For which figures work the best as the core offense in a Krennic list, Sentry Droids are one of your best options thanks to their long range prowess, which makes it easier to stay close to Krennic while attacking and he hides in the back lines. Snowtroopers and Stormtroopers also have pretty good accuracy and can be a huge tempo swing if you can get 3 attacks off all with power tokens. Heavy Stormtroopers also have good range and damage for their cost, especially if they have a reroll for their blue die from a Modular Targeting Computer.
Krennic's main weakness is his low health. You'll want to keep him alive at all costs, which can be tricky since his token doubling ability is limited to range 3 with an Advanced Com System attached. That means using body-blocking with your cheap troopers when possible and possibly having those Guardian figures protect him by using cards like Get Behind Me and Bodyguard.
Leave your comments below and discuss your thoughts and experiences with Director Krennic in IACP. See Krennic in action at the UKGE tournament: https://youtu.be/Pxn7NIbkTuY