Just earned this TODAY. I've spent many hours going for this one and would get 3rd, 2nd, 4th so many times. ...as well as getting killed early on. Here is my advise as well as some tips that will increase the chances of you getting into a game of mostly BOTS, which will make this SO much easier.
How to Increase Odds of Bots:
1. Turn off Crossplay, you can only do this from main menu before starting matchmaking. This way you are only playing with other people on Xbox, while others might be going for the same thing w/ same trick, I can tell you it certainly does increase bots. It will also increase the wait time to find/create a match, so get your phone out and download MS Solitaire or whatever to knock out other achievements while you wait. (Some matches took 5+ minutes load and then the additional wait in the staging area for the plane drop to start things off.)
2. In SOLO alternate between TPP (Third Person Perspective) and FPP (First Person Perspective). At the time fewer people tend to play FPP so selecting this combined with no xplay got me into a game where I only killed BOTS and got my solo win. I totally think this was a LOT of luck and timing.
3. If possible try playing at different times of day during the week. If you think about it, playing during business hours (I won at 11:30AM CST), eliminates anyone that can't get a round in during work hours. In the evening 4pm-12am it tends to have the most traffic. So mix up the times that you try playing and take note of when your wait times are longer and not.
Gameplay Skill Advise:
First off, I am not the greatest player. I have gotten a lot better at this game because I have been playing it a lot lately. I'm an older gamer (I started playing on a PONG system if that dates me enough), and I can definitely tell that my reaction time and thumbstick control isn't as good as it was 15-20+ years ago. I lose out a LOT...but I am good at strategy, and most of the time I can end up in the top 10 by thinking.
1. Don't get discouraged, every time you die or lose is a learning opportunity, it is also progress on the other achievements (unless this is the last 1 for you somehow, but by the time you get 1k kills you'll likely get this.) This game is ever evolving so things can open up in your favor, you never know when the next game you'll be matched w/ people that get bad gear and you get a perfect setup, or they are poor players, or like mentioned the are all/mostly bots. There is so much LUCK involved here, so keep that in mind.
2. Learn which Gear setups work best for you, for end game a DMR or long range weapon is critical, your alt can be an AR or SMG for short/mid range. I prefer a RedDot or 2x scope for closer range and a 3x/4x/6x for long range. If you have a good long range setup then a red dot is ideal for close up work to give you better field of view. Everyone is going to have their personal favorites, I'll discuss some of what I like in order of preference:
AR: M416 (L/M/S range Equip: Red-dot or 3x scope, Tac Stock, Quick Ext Mag, Supressor/Compensator, & Vertical Foregrip), QBZ or SCAR-L have similar performance, Beryl 762 (M/S range, Equip: Red Dot, Compensator/Supressor, Vert Forgrip, Ext Quick Mag) - hits harder but more recoil,
DMR: SKS (my fav), MK14, QBU, MK12 (if I find any of these I'm getting it as my long range weapon.
SMG: UMP45 or Vector: these are all short range some can almost reach mid range, but these are all pistol rounds they shoot super fast but each hit is low damage, great for close quarters combat but they need extended magazines, stocks, kit them out best you can quickly. ONLY way I roll w/ one of these is if I have a good DMR/AR as backup and for mid/long range.
3. STOP moving when taking shots, if you move while shooting your aim drops a TON and you will die. Just crouch, be in cover if available, and line up your shots.
4. Learn how to identify BOTs quickly. Their names will be more generic and will typically have an _ (Underscore) in them. Also bots tend to run erratically, they will run back and forth in a pattern, like behind a rock they will go from one end to the other, they will also be slow to return fire, sometimes not getting to cover. Bots are fairly dumb, and their aim is usually bad. For every shot they hit, they'll miss 3 or 4 times, so get some cover and find them line up the shot. Knowing bot vs human shouldn't change how you fight a whole lot, but you can be a little more risky depending on what kind of gear you have, odds are if it is a bot they will find you first and hit the ground or trees all around you before landing a hit. Humans will be sneaky, will get to cover and play mind games/strategy. They won't run in straight lines. Bots also will only have a very few useful items, they do not kit out a weapon. Bots also do not drive vehicles, if you hear/see someone on a vehicle, it is a human so be extra cautious.
Ok I had some more thoughts but they left my brain. I struggled w/ this one for a while and I'm so happy I nabbed it...now to focus on my other kill types/wins/grinds. Good luck! If you got this far, I really hope this helps and you get it! As always please let me know if you have other ideas to make this a better guide in the comments.