Killing someone entirely in Eclipse Phase is difficult, at least in the Inner System. Every time a person egocasts to a station there is a chance of a copy being made and interrogated. Every time a person goes through a secure checkpoint there is a chance of a fork being demanded and interrogated. Storage is cheap enough that putting a copy of your brain scan in an off grid, secure site (Like, under your mattress) is a trivial task. So the solution is that you don't kill them. You destroy them in much more subtle ways. Forknap them, go to town on their Ego, and remerge it with the original. Fiddle with it in ways subtle enough not to throw up any red flags (At least immediately), but powerful enough to potentially destroy their life. Rearrange their brain so that whenever they encounter someone they even potentially like they experience intense anxiety. While you are at, stick in a mental block that attaches seeking help for such an ailment with intense shame. Congratulations, you just destroyed that persons social life, and in such a way that it might go unnoticed for quite some time. If they live in a reputation economy it is even easier. At least in the Inner System such a person might get away with working the night shift. In the Outer System, they suddenly turned into a giant douche, and fuck that guy. Reputation goes down. If you are dead set on actually killing the person, you go the slow route. Cripple their Ego in such a way that it will not become apparent for a year or so. Edit their sense of the world so that they become a staunch bio-conservative, delete all their backups and go live with the rest of the Luddites (:D) in the Republic. Then you throw them out an airlock. Job done. In Eclipse Phase, psychosurgery and the subtle path is king. Shooting someone in the face might get them out the way for a week (And enforce an anxiety disorder or two). Playing the long game gets you results. Dealing with someone like a Sentinel is much, much, MUCH more difficult. A Firewall agent has the backing of an extremely dedicated organization that is basically entirely focused on keeping their people alive. Agents are accessed under the most stressful situations possible, they are put through trials that break most people with ease. And that is before they are told that they are even trying out. Firewall knows that their agents wont break, they have extremely intelligent people (and other things) coming up with ways to check. So all you can do is try to discredit them. And the only way you can do that is by being part of the Org. And if you are part of the Org, why are you trying to discredit them (and why doesn't Firewall know)?

I happen to like the quick and dirty shoot em in the face style. But it all depends on your motive and time frame. If you're motivated to eliminate them from the universe but you're pressed for time; 1. get access to a healing vat and an ego bridge 2. shoot them in the face in some way that that evades detection and suppresses their muse as a witness. 3. Heal the body and sleeve yourself into it. 4. go to their backup insureance provider(s) and get backed up. 5. go steal their secret backups from under their mattress. 6. Hide the body. If you have access to mad Hacking skilz. 1. find and hack their backup insureance provider. Kill the backup. 2. call them to let them know that there has been a problem with their backup storage and schedule an appointment to have a new backup made. 3. pay someone to ambush them on the way to get backed up. (4.) alternately if you have access to the insureance provider at the right time you might be able to kill them and their backup with the Ego Bridge.