强悍 is almost always a compliment - it conveys admiration for someone's toughness or power. It's used for people, teams, performances, and abilities. Stronger and more vivid than 强壮 (physically strong).
mistakes
Don't confuse 强悍 (tough/formidable) with 强硬 (hardline/unyielding). 强悍 praises raw power and toughness; 强硬 describes an uncompromising stance, often in politics.
