Is it possible to kill everyone in Oblivion?

Answer 1

no. people that don't die and only get knocked out do so for a reason. they are part of a major quest.

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okay i just decided to keep his idea up there, but heres a more detailed explanation

you cannot kill them either because...

1. they are part of a important quest
2. a important person (like when fighting with somone important like martin or jauffre)
3. they are a owner of a shop or guild

now i think those are the reasons, but there are ways to kill them (i think)

1. you could probably find a mod that allows you to
2. use the console to kill them

thing is with the console you cant really kill them with your weapons, it'l just kill them where they stand lol.

Answer 2

No. Guards will continuously respawn forever. Some guards such as the invincible one in chedinhal and other guard captains can only be knocked down. Most civilians are killable but there are a fair few who are considered essential characters and are therefore invincible.