Relentless Killer
Earn 10 Relentless medals (Get 20 Kills without dying).
Brutal Killer
Earn a Brutal Medal (Achieve a 25 Killstreak)
Frenzied Killer
Earn a Frenzy Kill medal (5 Rapid kills).
Chain Killer
Get a Kill Chain (Kill over 7 players rapidly).
From the Depths
Get 25 Kills with primary or secondary weapon whilst underwater, whilst the enemy is on land or a ship’s surface
Hard Wipe
Eliminate an entire squad of 4 players in a Fireteam mode.
Underwater Ops
While underwater, plant C4 on an enemy-occupied Gunboat or Wakerunner, killing a crewmember. Do this 5 times.
Nuked Out
Earned a Nuclear medal in Free-For All without using Scorestreak rewards.
Back At You
Return a Frag Grenade to sender and kill the enemy that threw the lethal projectile at you.
Very Nuclear
Earn a Nuclear medal with 25 different weapons, with all kills coming from that weapon.
Nuclear Killer
Earn a Nuclear Medal
Mega Kill
Earn a Mega Kill medal (Get 6 Rapid kills).
Dark Ops Master
Complete all Dark Ops challenges.

Very Nuclear sounds rough. I end up sticking with a single gun or two until I unlock everything for it before moving on.

my understanding of tghta challenge is you have to get 25 nuke medals (30 kill streak all from the gun) each medal using a different gun

   Thanks Mr T for all the info you have provided on CW lately. It's
been a big help.