So me and a friend of mine, who plays a psyker were discussing force weapons, and how powerful of a weapon they were. He was not aware that daemons do not get the double toughness vs psychic powers and force weapons. We are not at the point in our campaign where im going to be throwing hordes of daemons at him, but he mentioned using it in a big boss battle, and that got me thinking. How would you balance out a fight where your party has to fight a large daemon (lets say this is like the final battle). Psykers are very good at dealing daemons. they do a lot more damage then other classes to them, and have high willpower to resist fear. While I am okay with the idea of psykers doing maybe more then average damage, I still want the other members to feel as if they are impactful in a fight.
Im pretty new to DMing, so im not very experienced in this, so does anyone know how I could write (If I so felt the urge) to write up a big battle with a daemon with a psyker where I dont run the risk (If there even is one) of the psyker stealing the spotlight?