Comment by DaiPlusPlus

> How many chat systems does google have?

* Google+ (rip)

* Google Allo

* Google Chat

* Google Groups (separate from Google's Usenet service)

* Google Hangouts

* Google Messenger

* Google Duo

* SMS via Google Project Fi

* Google Voice

> And how many dozens more have they already killed?

Too many: https://killedbygoogle.com/