Denshi Jisho — Online Japanese dictionary

Found 4 sentences.

初め一歩唯一難関 The first step is the hardest.
第一難関どうにか突破した We have managed to overcome the first obstacle.
持ち前頑張り精神難関突破した I got over the difficulty with my characteristic tenacity.
中学生英語学ぶ難関一つ関係代名詞です One of the greatest hurdles facing middle school students learning English is relative pronouns.