In June of 2019 R6 Siege underwent an achievement overhaul. A total 33 of 49 achievements were changed.
"Terro Hunter - Kill 2500 terrorists in Terrorist Hunt
" was replaced by the current achievement Accessorizing
which requires you to equip 50 weapon attachments. All attachments are unlocked by default. You can enable the achievement tracker overlay to make sure you're getting progress.
Go to Operators > "Any unlocked Operator" > Loadout > "Main Weapon" > Sights.
If you hold right on the D-Pad and continually tap A you'll get the achievement very quickly. There's need to cycle through multiple Operators or weapons. Thanks for writing in, @Pending Demise
For all the TA historians out there I'm leaving my original solution below. I'll be seeing you good folks at the LVU Campus!
A few fellow TAers had asked me for a method. Here it is.
N.B. Metalgear2k2 reports that his kills didn't count if the t-hunt mission failed. I'm quite sure mine did, on launch week though. Keep an eye on your achievement tracker!
Mode: Classic Terrorist Hunt, Lone Wolf, Normal difficulty
You can set the matchmaking preferences by pressing start in the main menu (see the icon on the top right of your screen). Cranking up the difficulty puts you against more enemies and gives more XP but it's not worth the risk of dying mid run.
Map: Presidential Plane
Easy layout, consistent Bomber spawns, narrow corridors and an even distribution of enemies. Go in through the main entrance! That often spawns in bombers that run towards you down the aisle on your right. You definitely want to take on the big guys at the beginning of any run.
Proxy explosives are a concern. Sometimes they detonate behind a wall and still deal heavy damage. Thatcher's EMP grenades serve as a counter. They're excellent at quickly clearing out choke points littered with explosives. Stat wise 2* armor and 2* speed is a good mix.
Loadout: Enfield L85A2, MK25 pistol, stun grenades
Two AR options here: I went with the Enfield. K33 is mediocre because of the lackluster fire rate and small clip. ARs use large cal. ammo which helps you get penetration kills too. The MK25 pistol strikes a good balance between damage and capacity, but at range it's headshots or nothing.
Gameplay tips for T-Hunt
Turn up the audio. You're going to want to listen for Bombers and proxy explosives. Both emit a warning sound.
Lean and peek around corners, especially when you know there are enemies waiting on the other side. It's safer. Also, stun grenades, use them. They can be tossed in barricaded rooms through the small gap at the bottom.
Slow is fast. If you die mid run you lose out heavily on xp & renown and are forced to sit through loading screens.
Last 3 enemies rush you. Camp inside a room with only one entry point. You're most likely on low health and definitely do not want to die here.
If you're struggling to complete solo runs, you might want slow it down and try using Fuze.He has more armor and can even bring a shield. For me personally the 1* speed felt too sluggish, especially against bombers.
True to R6 form FAMAS is an excellent AR! To spice up the grind I went with Twitch on occasion. The statline of 2*/2* is solid. Her drone is useless and P9 as a sidearm is rubbish. But that FAMAS though!
If you're looking for an even faster way to rack up t-hunt kills, you could try the map House. The layout is more compact versus the Plane and it does get very hectic at times when enemies come from multiple angles, but with enough skill it's possible to finish a solo run faster.
Time wise you could fit anywhere between 7-12 finished solo runs per hour including load times, which gives an average of 250 kills per hour. MAKA91 reports he averaged 4:00 - 4:30 incl. load times (290+ kills /hour).