Chariot

TurdBoi's solution is great but I made a video of me completing it solo.
Good for those with only one controller (like myself).
I completed it with the magnet, mine is upgraded twice, but I'm pretty sure you can do it with a magnet upgraded once.
Found the magnet-gadget in world 3 and 2nd upgrade in world 4 and 3rd upgrade in world 5. I'm not too sure about the the specific locations, if anyone knows, please let me know and I'll edit it.
Nothing else to add, just follow the video and for the tricky parts, place the chariot where I place it and the achievement will come without too much effort.
Good Luck :)

DLC required.

Post the release of The Royal Gadget Pack DLC this achievement is super easy.

Equip the Warp Beacon (available immediately after buying the DLC) and load up 1-1, then just progress through the level normally without using the rope. When you reach a road block, more up or over the obstacle without the chariot then press to plant the beacon then again to warp the chariot.
It takes 20 seconds to recharge the ability so you might occasionally have to wait a few seconds.

Just managed to unlock this solo using 2 controllers. I am unable to post a video of my run through as I don't know how, but if anyone wants more info on how I did it please message me over live.

Start off the level (Woodland Vestibule 1-1) with 1 character's item as the magnet and the other character's as the repulsor. There aren't to many difficult parts in this level and alot will be trial and error. I found it easier to always position the character with the magnet equipped in the elevated positions, jump with this character and then press to attract the chariot towards you, now with the second character use the repulsor while the chariot is still in the air to repel it to the elevated platform (unless you are able to place the repulsor character directly underneath). Where possible stand directly underneath the chariot and use the repulsor to send it directly up in the air. Then use the magnet to pull it towards you, this way is much easier as the chariot takes a controlled path as opposed to a random one.

Sorry its very vague but I hope this helps, as a side note the items I used were not upgraded at all, so it may be possible to do this solo with an upgraded magnet. (I will be checking this theory once I have found all upgrades).