The Texas Chain Saw Massacre

Sooooo after completing this achievement in Public matches without boosting, here are some tips for those who also are looking to complete this achievement.

Now first of all this achievement is a huge pain due to executions occurring upon dealing enough damage to a Victim. You'll have to do a few hits then just chase and hope the Victim does a lot of rushed actions such as crawling through walls or vaulting over destructible barriers to hopefully get them into incapacitation.

Next another thing to note is once the Victim is incapacitated wait until they go from laying on their back to laying on their front. For some reason if you don't wait for them to turn around the game doesn't let you carry the Victim it only gives you the option of execute, so just wait over the body until the carry prompt appears instead.

Now for your Leatherface build I recommend getting your Maim ability to Level 3 just so you can constantly turn your chainsaw on straight away. Now for skill points go up the middle skill tree to unlock Leatherface's perk "Rough Cut" At level 3 it's effect is "Hitting a Victim with the chainsaw causes 1 HP of extra damage per second for 7 seconds." Now it doesn't exactly secure you the downs but it helps get those extra little bits of chip damage to hopefully cause an incapacitation instead of an execution. Dump all your skill points into Savagery and Endurance, also grab the Grandpa perk "Windoom" I shall be talking about why this will be useful in just a moment.

The best map to try and get this on is Family House (Out of my 10 executions 9 were on Family House) so I would recommend just keep searching for lobbies for this map just to make your life easier. The reasoning to use Family House is due to the windows as if a Victim jumps out of a window whilst they have low health they will become incapacitated so you can quickly go and pick them up once you've seen/been alerted by indicator of if a Victim went flying through a window.

However, even with all this setup it still requires a lot of luck and for everything to line up in your favour, the issues you may come across are:

1. Your fellow Family players may come zooming in to execute a Victim before you get the chance to pick them up.
2. Upon Executing a Victim if they're to disconnect then much like other Achievements requiring kills, upon disconnecting it doesn't count as you killing the Victim so you won't get tracking towards this achievement (This happened about 7 times in my time trying to get this achievement)
3.Upon picking up a Victim you have 30 seconds to get to a highlight Gallows so just be aware you'll need to try get there within this time restraint. (This never was an issue in my experience but can see it possibly being an issue)

Hope this helps anyone trying to get this achievements!
But my biggest word of advice for this and some of the other annoying achievements is just boost them in Custom games. :)

Family House is the best map this, as for getting it in public matches you really need the stars to align. You need a victim to not only jump out each of the three windows, they also need to be injured enough beforehand so that doing so will put them in the recovery state. Once they're picked up, there's 3 gallows to choose from and each has a specific route you should take. If they jump from the top floor window into the backyard, carry them to the one in the kitchen. If they jump from the side window, there's a gallows in the little shed just in front of it. If they jump through the front window, there's a gallows at the shed where the generator can spawn.
Make sure the doors on the path to the hooks are unlocked! You can open them if they're unlocked while carrying but I'm not sure you can unlock then.

Notes:
1)The hooks will be highlighted for you no matter the distance.
2)For whatever reason, a gallows execution doesn't count towards the Serial Killer achievement.
3) if possible this can be done with assistance by your teammates if they have perks/abilities that cause damage over time and/or perks that highlight victims. Perks like Hitchhiker's Venom (30 points of damage over 30 seconds at max on victims caught in his traps) can help down them. Obviously I'd recommend being in a group if going down this route.
There is a grandpa perk that increases damage to people jumping from a window but you'd need to level him the appropriate level AND hope he doesn't get stabbed.