To defeat Croker, look at the objectives in the top left of the screen.
Make matches that are shown in the objectives to damage Croker's health bar.
For example, on level 361, see the mission on the left hand of the image with a red square.
You have to pop Vertical Line Balloon, Horizontal Line Balloon or a Combination of these two to attack Croker.
How to make the Combination of Vertical & Horizontal Line Balloon?
Click one of Line Balloons and move it to another one. Wow, you made it!
Please remind that the mission objects may differ on each Croker mode.
Hope you defeat him💥👑