Sometime they have a featured Lootcase which increases the chances of pulling the featured character, or you could try pulling them in 5 star lootcases
There is 3 options: 1. Grind out around 6000 5 star lootcases to earn a chance at him in a 5 Star lootcases 2. Grind out around 10000 5 Star lootcases to have an higher chance of getting him in a featured 5 star lootcases 3. Wait for him to have a featured pack and purchase his Lootcase which will give you 7 lootcases each with a 25% chance of pulling a 3 star, 4 star, or 5 star with the highest star being the lowest chance