行径 is a noun that almost always carries a negative connotation, referring to a course of action or conduct that is bad, objectionable, or despicable — like 'behavior' in English when used critically (e.g., 'such behavior is unacceptable'). Its original meaning of 'path' or 'trail' is now rare in modern Mandarin; you will almost only encounter it in formal or written contexts describing someone's reprehensible deeds.