Scary
Fearful
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 fear? When you feel fear, you think something is scary.
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: How scary is it? It's Oh so (おそ) scary!
恐ろしいと思うかもしれないが、自然の法則には逆らえないんだよ。仕方がないさ。
You may feel scared, but you can’t defy the laws of nature. It’s no use now.