Answer:
1. Spirited does not belong
All of these words have to do with something that is bad and unpleasant, but spirited means enthusiasm.
2. Indignant does not belong
Indignant is not a word that goes with the others, because it doesn't mean being inventive.
3. Interjection does not belong
Fatigue, exhaustion, and lethargy all have to do with being exhausted. Interjection is the act of interrupting someone, with doesn't have anything to do with exhaustion.
4. Courge does not belong
Courge is a food, while the other words mean a disease.
5. Peevish does not belong
Peevish is the only word of this set that does not belong because it does not mean irritable like the rest of them do.
6. Incoherent does not mean "not decent," like the rest of the words do.