I’ve made a few of these. Varying degrees of “standing still” will get you different results, but I’ve beaten all of the game’s content except celestials with
this: Dervish, Level 100 (GD 1.2.1.3) - Grim Dawn Build Calculator
And this: Trickster, Level 100 (GD 1.2.1.3) - Grim Dawn Build Calculator
…And also this: Blademaster, Level 100 (GD 1.2.1.3) - Grim Dawn Build Calculator
And while this one is more active than just “standing there”, it has a LOT of player-scaling pets at its disposal and can beat most celestials (Couldn’t do crate and Calla, but that may be just a skill issue) : [1.1.9.6] Bloodbound - Pseudo-Pet Skater Bleed Dervish [Cr] [SR80+] [Ravager of Minds, Mogdrogen]
There are a lot of variations on the theme, and any combo that includes Oathkeeper, Shaman and Nightblade can potentially accomplish that. Blade spirit in particular stands out as the most powerful of the bunch.
The passivist thread that @Bas linked above has a host of experiments and a lot of them use player-scaling pets to do the heavy lifting.