I found this game's honour mode to be less fair than the first one, so I had to resort to using Barrelmancy. This is when you take an unbreakable container and fill it with lots of heavy items and use telekinesis to drop that container on enemies. It only costs 1AP to use telekinesis and when the container is heavy enough it can do ~5000 damage. For comparison, at the end of the game, my attacks were doing in the high hundreds of damage and used 2AP each.
First of all it is important to have your characters set up properly, as you will want your main character to have high persuasion (to hopefully avoid a lot of fights), as well as having a character with loremaster, and another with thievery (preferably an undead).
For attributes, everyone should focus on Wits for high initiative, then a secondary stat, I suggest Strength on your main character so you can carry more things, also, having a bow user who focuses on Finesse can be nice when you have to destroy objects. Everyone should also put a couple points into Constitution so that they hopefully can survive a hit or two.
For combat abilities, you will want 2 points in Aerothurge, Huntsman, and Warfare for the movement abilities Nether Swap, Teleportation, Tactical Retreat, and Phoenix Dive. Using these skills to move around the battlefield is much better than just walking.
For civil abilities, your main character should focus on Persuasion, you should have an undead focus on Thievery (so you dont need lockpicks), and a throwaway character should focus on Loremaster, with fourth character focusing on Telekinesis right away. After those abilities, everyone should focus on Telekinesis. Once Telekinesis is about level 3, battles will become very easy, and higher Telekinesis makes them even easier.
For talents, your Persuasion character should definitely have Pet Pal. Other than that, useful talents are: Executioner, All Skilled Up, Bigger and Better, and Comeback Kid.
The setup for the majority of the game is that you will have a character that cant move because they over-encumbered, and the other 3 party members will participate in combat. As long as you keep the over-encumbered person linked to the main party, you can select them and warp to a waypoint to bring all 4 characters. Also, having this person unable to join in combat means no fight can ever truly cause a game over. There are very few fights where this character will be dragged in, and for those you do need to be careful.
Gear does not matter too much, though you do want to focus on finding things with +Telekinesis on them, and towards the end of the game you should have plenty of gold to buy equipment with enough armor to keep you alive.
Now for actually getting your container set up. The earliest/easiest unbreakable container is available immediately upon entering Fort Joy. If you leave out the south exit and head east to coordinates x:262, y:97, there will be a dirt pile that you can dig up to reveal a hatch. Inside that hatch at coordinates x:188, y:562, there will be another dirt pile that you dig up with an unbreakable ornate chest. Pick this chest up and send it to whichever character is your throwaway's inventory.
Now that you have the container, it needs to be filled with other heavy objects. I only bothered with objects weighing at least 50kg, like Oil, Water, Ooze barrels, large paintings, packages, and metal crates. Plenty of these can be found around the Fort Joy area. Once your chest's weight is ~500kg, it becomes quite effective in combat. The final weight of my chest was 10,000kg and it did ~5000 damage with each move. (in order to actually put things in the chest, in the inventory screen, click the right stick to enable multi-select, select all the things you want to put in the chest, then press X on the chest and select put into).
This chest should always stay on the character you dont plan on using, and when combat starts, open the inventory screen, send it to whoever's turn it is, then drop it (this will use 1 AP). You can then press X on the chest and select the move option, and then choose where to put it, as well as rotating it with the left and right bumpers. You need to place the chest kind of precisely, ideally the chest will be physically on top of the enemy, but sometimes that is not possible. Trying to place the chest on the opposite side of the enemy seemed to help. DONT FORGET TO PICK THE CHEST UP AND SEND IT BACK TO THE THROWAWAY CHARACTER AFTER EACH COMBAT.
There are a few fights that can be a bit worrisome. Some of them are the ones where your fourth character is forced to participate, but you just have to be a little more careful in those. There are also a couple fights where an enemy has an evasion aura. For those fights, if an enemy has that aura you will only have a 10% chance to hit. Just keep moving the chest until you get a hit and they die. There was only one fight that killed all 3 of my characters, and it was against Karon in the sewers at the end of the game, he killed all 3 of them before i even got a turn.
Something to keep in mind is that in the arena area in Driftwood on the Reaper's Coast during the second part of the game, there is a person who can give you an Idol of Rebirth, Dorotya. You have to accept her gift and choose the last option (the one about a butterfly and a chrysalis iirc). This item is very useful, and if it ever gets used in a fight, make sure to craft the Ashen Idol with a Resurrection Scroll to make it usable again. While you should never be in danger of game over-ing, this item can help speed up some fights.
One last note is that if the area you are fighting in might become inaccessible, make sure to land the final kill AFTER picking your chest back up. It can be a pain to find unbreakable containers AND have to refill it with heavy items. The places i remember like this off the top of my head are the arena fights and the fight on the boat after leaving Fort Joy. There may be more, so if youre not sure, make sure to pick up the chest before ending the fight.
Overall, this playthough was VERY easy and there were very few parts I was actually worried. Most of that worry came from not having all the movement skills i listed earlier, which would have made some fights MUCH easier. Also, more Wits means you get your turns faster, and there were some fights i didnt get the first move.
With all that said, if you REALLY dont want to actually do this playthrough, I have my save, so just shoot me a message and if im on i can load up the game and give you the achievement, it takes like 5 minutes.