Betrayed by his friends, he started living alone.- Here “Betrayed” is a/an-

 Betrayed by his friends, he started living alone
-এখানে বাক্যের সইতে Betrayed past participle হিসেবে ব্যবহৃত হয়েছে।
-  Perfect participles are formed by combining any past participle including had with the word having.
- Example: having asked, having broken, having grown, having placed, having told, having worn.

Source: Advanced Learner's Grammar and Composition by Chowdhury and Hossain