Check:
https://securemessagingapps.com
and rate the security
green=3 yellow=1 red=0
Results:
1. Threema = 85 = most secure messenger and paid by the users (+bitcoins)
2. Session (Loki Coin) = 79
3. Signal / SignalApp = 77
4. Wickr (Amazon) = 62
5. Element / Matrix (Amdocs)= 59
6. WhatsApp (Zuck) = 34
7. Telegram (Putin) = 29
8. Apple iMessage = 25
9. Facebook Messenger (Zuck) = 25