Quickly removing 100s of contacts

[laurisplus]

After transfering contacts from my old iPhone to my new Nokia Lumia 1520 I have ~2500 contacts in my phone. I would like to delete 90% of them. How can I do it the fastest possible way?
These contacts are connected with both Google and Outlook.

 

[Microsoftjunkie]

Probably faster through Outlook.com.

I had alot of contacts and there wasn't a fast way on the phone. . Since WP backup all contacts to outlook.com there maybe a faster way.