If that's what we need to do.
Lionel didn't die because we wanted him to, we needed his help on that mission and we wanted him to return alive from it.
Mauve didn't die because we wanted her to, she died because she opposed us and the best way to stop that then was to kill her.
Mauve didn't die violently because we wanted her to, that needed to happen because of what was going on at the time.
Sometimes the best possible answer is to kill. Sometimes, the best possible answer is to not kill. What matters more than killing, more than suffering, is the mission.
Sometimes the mission is to kill. But that is almost always for a goal, to attain something else, something grander than death, better than suffering. Just like you work towards making a staff, and you keep working towards making that staff despite anything that happens to stop you - but you don't stop, you just start over again, and again as you need to.
Killing someone is usually like one attempt to make a staff. It's not the real goal. That attempt didn't matter, if that person dies or not doesn't matter. What matters is that you're going to continue to try to make a staff, and you're not ever, ever going to stop until you succeed. Controling people, even people you want dead, is usually the far more empowering answer. Getting a value from the rest of their life in your service is usually a far greater return than gaining another corpse. Even the depths of suffering that can be attained over a life in your service is, almost always, in far greater excess, many multiples of excess, than what can be attained by any single death.
But there's another thing that matters. You don't only try to make the staff. You also live and play and enjoy and learn. You consider, you judge, you choose, you select.
Setting killing your ex-teammates as a goal is much like making your goal be... to just go stand in a corner. You -can- make that choice, but why? It gains you nothing. It helps not at all. It actually costs you, and without empowering you. Even if you convince yourself that you -do- want to just stand in the corner and stare at the wall, all the time you can spare, every chance you get - that's wasted time, every second you waste upon it.
I would prefer you to set goals that empower you, that help you understand the world and what you can do with it better, that help you understand your limits, others' limits, and how you can work with both - how you can sometimes change either. If you set your goal to be standing in a corner, or killing those ex-teammates; well I will call you out of that corner and set you to meaningful work, to a better use for your time, and I urge you to consider and try to understand why a focus upon those ex-teammates' deaths is as worthless to you as a desire to go stand in the corner would be.