I can't do anything halfheartedly. I have to do everything 100 percent.

我做任何事情都不能半心半意。我做每件事都必须百分之百地投入。

《柯林斯英汉双解大词典》

Honestly, I didn't really care, and ended up doing it 2 halfheartedly.

坦白地说，我并不是很用心，最后只是敷衍了事。

youdao

Neither of you do anything halfheartedly and you both have strong, powerful convictions.

你们没有一个会三心两意，你们都有强壮、有力的信念。

youdao

The political conflicts culminated in a landmark joint statement with the government in January to set a 2% inflation target a policy Mr. Abe had advocated, but one Mr. Shirakawa appeared to adopt halfheartedly.

WSJ: Departing BOJ Governor Shares Doubts on New Policy

Apart from an idle man halfheartedly flipping through a book of local attractions, there was no one in the front of the shop, where miniature carved boats and model fish aged unwanted on the shelves.

NEWYORKER: Alone