[zycynynq] That's no small galaxy

That's a K3 civilization coming to attack us.

Inspiration: Before obtaining the Infinity Stones, Thanos was trying to kill half of all life in the universe the hard way, with an army.  Realistically, to do that, he would have needed a fleet at least the size of a galaxy.  (Probably more: the universe is a large place.)

It seems fairly straightforward to move a galaxy: stars can be steered, for example, with a Shkadov thruster.  Use massive stars to gravity assist smaller, less powerful stars, as well as shepherd gas and dust.  Supermassive black holes (and black holes in general) can produce lots of energy by dropping stuff into them, so some Shkadov thruster variation should work on them.  How do we move dark matter?