Flag Runner You must win 50 CTF matches, joining in the middle of a winning match you do get a win.
The first method I will say is if you want to get this by playing normally and get 50 wins while going for the objective. I have been doing this method for a bit and it seems to be the best if you don't want to join any boosting sessions.
What I did was join a match and if my team was winning I stayed, but once my team loses, I would leave and search again. I have won about 10 in a row with a group because I stayed with people who actually cared about getting the flag or defending it, other than people who are looking for kills (or just are bad at the game, no offense to those who are) but that is why im making this guide to help ALL get this achievement!
Now once you found a winning game and keep playing until they lose, I would recommend guarding the flag, and one of the best tools to use is the ARC mine, just place 2 next to the flag and sit in a corner looking at the flag. Usually people try to run in there as fast as possible to grab the flag so just use your weapon of choice to kill them, and do the best you can. Make sure to always drop your titan and use your burn cards to your advantage.
[BOOSTING METHOD]
This other method can be a bit annoying but it is the fastest especially if you get it going.
Trueachievements has boosting sessions if you go into the boosting session category (or add this game to your boost list) If you host a session, just follow this guide and you will get some fast wins. Create a party and get 6 of the people in it, then create another party and get the other 5 in it, (12 people in a session 3 as back-ups) Have 1 person be the party leader and control that group as you control the other.
Once this is done, both leaders change their servers to JAPAN WEST in the Main menu, then invite everyone in your parties to the games.
When both groups have 6 people in both groups, just search on CTF at the same time running into each other. Once you find each other and the game starts, the team losing first just back out. Once back on the menu, start searching again to run into the group again and alternate wins.
Note: According to Snowed she encountered a problem with running into each other. The solution to that problem was everyone searching and running into each other individually. The only problem I can say about doing this method is the teams will be always random and you cannot make it completely fair to taking turns on the wins.
Any questions or comments? Please comment or send me a message, good luck and have fun!