There is no question that the Flathead, or Yellow Catfish (Pylodictis olivares) is the moodiest, most cantankerous, and definitely the most aggravating catfish there is. And the bigger they get, the worse they get, and they get huge.
Flatheads differ most other catfish in that they have a flat tail, rather than forked, and a pointed wide head. They look more like a bullhead on steroids than a channel cat. Although they can be found in lakes, they prefer slow backwaters and eddies in rivers. They will usually find a hole somewhere, and just sit in it, and refuse to leave to get food. They would rather let the food come to them. They are exclusively fish-eaters, so dough and punch baits will be ignored. They are also very moody, and will refuse to take a minnow even if it is right in front of their mouth at times.
Flatheads can exceed 4 feet, and 100 pounds, so when you do get one to bite, you have a fight on your hands.