To Pessimize

1. (transitive) To take a pessimistic view of; to speak of in a negative or pessimistic way. Antonym: optimize
2. (transitive) To make (something) pessimal or the worst; (in a weaker sense) to make (something, such as a computer program) less efficient. Antonym: optimize
3. (intransitive) To think like a pessimist; to believe the worst. Antonym: optimize
4. (intransitive) To become pessimal or the worst. Antonym: optimize