How dangerous would a Stelaser be?

So assuming the following, a Stelaser is build that can, at max, push a Ship with a Mass of 3 Megatons at 2G for several weeks if need be.

Needless to say, that’s a stupidly powerful and concentrated Laser. Due to this, the current version of everything puts the launch points for the ITV´s far away from Earth on its own orbit, where there is nothing in-between the ship and the laser. At least for the acceleration phase.

Thus the question becomes just how much damage such a laser could do if it, by accident or as an attack, is used to burn stuff on Earth or anywhere else for that matter ?

My own thoughts

Considering just how much light you need to capture and focus on a more or less small point, I cant see any structure surviving this for any amount of time. At least as long as it isn’t built to do so. The sails on the ship itself obviously do handle it pretty well.
I am pretty sure that the heat, radiation and brightness together are well above what you need to just melt your way across, or through, anything you want. But the scale is kind of out there. If we for example say that the Main Mirror somehow shifts a fraction of a degree, the beam itself would pretty much rampage across Earth at light speed. Entire cities would be there one moment and then gone the next. More or less like a chain of nukes.

But yeah, let me hear what would happen and how much damage it would do 😀

Thanks for the help !