Unless it has been changed, you only need to be in the last mission to get the badge.
I've used this to my advantage a few times before Posi TF revamp. I used to start the TF with my two accounts and a friend, then log one of my characters out and do the TF until last mish, then log the other character on and get badge on both of them.
- @DSorrow - alts on Union and Freedom mostly -
Currently playing as Castigation on Freedom
My Katana/Inv Guide
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. -Einstein
The group of people I normally play with tell me that to get the badge and reward from a TF now youi have to enter every mission.
I've tried searching the patch notes and the forums, but alas my search-fu is weak today.
can anyone cobfirm this is now the case or point me to a post on the subject. Cheers!