The Surprising Ways Mars is Hostile to Life

Deploy a gigawatt rated nuclear reator on mars, then use it to create a stron artificial magnetic field over the colony. With Starship or the much bigger Starhip 2 that may follow we would easily get a gigawatt  reactor up there. It doesnt need much shielding, just bury it in the ground deep enough, like in lava tubes or place it at the wall of the  craters. Use explosives to collapse the crater walls above it so its buried and shielded. It just has to be strong enough to withstand the rocks falling on it. 


Use multiple of these on the crater walls, and shield the whole thing agains cosmic rays and charged particles. And you may even create a plasma cieling to trap a high pressure (1 bar) earth like athmosphere in there. 
Span wires over the crater, create a mesh. Use sufficient power that any gas coming near this mesh gets ionized. Then the magnetic field will hold this plasma in place, creating an air tight cieling wich also shields charged particles and cosmic rays to an extend. 


And dont worry about nuclear waste - > just change craters when the power runs out after a few centurys. 


Yes, Mars is inhospitable. But we can test and perfect it on the moon, wich is even more inhospitable and then move on. Starship and what follows opens up so many possibilitys... Humanity has to use them.