Many Bomb King players lay "traps" throughout the maps. When you see sticky bombs on the floor or on walls, shoot them to destroy them! They take no more than 5 bullets to destroy and can save a teammate from walking into it and getting blown up.
Pay attention for his "Poppy Bomb" usage. If you see BK landing with low or even half HP - try to pressure him. BK can't use his escape for next 6-8 second, that would be enough time to kill him.
Due to Bomb King's significant lack of ranged attacks and abilities, any sniper or long range champion like Cassie or Lian can counter him quite easily. Just make sure you block all side routes, because Bomb King can very easily sneak in.
Frontliners Tip
Use your "CC reduction" card + "Resilience" to deny point pressure from "Grumpy Bomb".
BK feels relatively safe you while stunned. "Jumping out" of stun earlier, works like surprise effect & confuses him.