Is it possible to reset stat points in Torchlight 2?

There's no in-game way to reset your stat points, so your best bet is via a mod. My suggestion would be to use the Rapid Respec Mod. I've used it before and it's very handy. This will allow you to respec your characters stats and skills without having your character marked as a cheater. It comes with a Windows installer, so it's really easy to set up.

If you do use the mod I'd suggest turning off Steam Cloud Saving for Torchlight 2:

Turning off Steam Cloud Save is strongly recommended. Steam Cloud Save does not always respect the timestamps on files. This causes it to sometimes overwrite a save file that you have just edited with Torchlight 2 Rapid Respec with an older version of the file from the cloud.

You can do this by modifying your shared stash save file. Replace you shared stash save file with one that is full of skill and stat respect potions. The file is available here. The instructions go like this:

1. Exit the game
2. Backup your shared stash save located in: C:\Users\< username >\Documents\My Games\Runic Games\Torchlight 2\save\RandomNumber. It will be called sharedstash.bin
3. Download the file in the forums and move it to the above location.
4. Open the game, load a character and copy as many potions you want into your character’s stash and inventory.
5. Close the game and restore the backed up shared stash file.

You will now have your original shared stash and the skill reset potions. Using this method you will not be marked as a cheater and you can continue to use steams cloud saves. The file in the above link will contains:

• 396 potions of -1 vitality point and +1 unassigned stat point
• 396 potions of -1 dexterity point and +1 unassigned stat point
• 396 potions of -1 strength point and +1 unassigned stat point
• 396 potions of -1 focus point and +1 unassigned stat point
• 24 potions of reset all stats. Each stack of 99 is actually only one potion.

If you are having issues try disabling steam cloud saves after step 1 and re-enabling them after you restore your shared stash.