A sentence with 了 le (= particle) at the the end is negated with 不 bù (= not).
他 | 不 | 喜 | 欢 | 米 | 饭 | 了 | 。 |
tā | bù | xǐ | huān | mǐ | fàn | le | _ |
he | not | happiness | joyous | rice | food | particle | _ |
he, him, other | no, not, after negative question: yes | like | cooked rice | grammatical particle of time | 。 | ||
He doesn't like rice anymore. |