Bad
Poor, Wrong
い adjective
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of bad? It's also bad.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
Do you know how in the Mario universe all the bad versions are called "WARU" (わる)? For example: "WARUIJI" and "WARIO." That's because they are bad. They come from this kanji. So, if you ever need to remember this reading, just think back to Wario and Waruigi.
あそこのレストラン、味は良いけどサービスが悪いよな。
The restaurant over there has good food, but the service is bad.
悪い夢でも見てるのかと思った。
I thought I was having a bad dream.
牛乳は悪くなっていたけど、俺は気にしなかった。
The milk went bad, but I didn’t care.