Fastidious refers to someone who is meticulous, demanding, and difficult to please, especially in regards to food, taste, or standards.
Inflammable: This word means capable of being easily set on fire or ignited, and has no relation to being hard to please.
Incorrigible: This word means someone who is unable to be corrected or reformed, often in a playful or mischievous sense, but doesn't necessarily imply being hard to please.
Deteriorate: This word means to become worse or decline in quality, and has no relation to being hard to please.
