反而【fǎn'ér】

反而 introduces a result that is the reverse of what the first clause should have led to. It goes in the second clause, after the subject and before the verb.

不但不…反而

The fullest form spells out the expectation that failed, then the opposite that happened.

There has to be an expectation

反而 needs a cause that pointed the other way. Choosing tea over coffee is a plain contrast, not a reversal, so it doesn't take 反而.

• × 我不喝咖啡，反而喝茶 → 我不喝咖啡，喝茶

After the subject

反而 is an adverb, so it can't go in front of the subject.

• × 反而他更忙了 → 他反而更忙了

却 also marks a turn in the second clause, but only "yet"; 反而 says the outcome reversed.