[bluebrain]

I have added some admins to my server with some flags except 'root' and 'slay' flag, but still admins are able to sm_slay people. What should I check; or to resolve what should I provide with?

[MasterOfTheXP]

Have you restarted the server or used sm_reloadadmins?

[Bacardi]

Look SourceMod logs...

[TnTSCS]

I get:

[SM] You do not have access to this command.

When my steam has the following flags (I use admins_simple.ini because, well... it's simple ):
"STEAM_0:0:266" "99:abcdeghijklnopqrst" //TnTSCS

Are you giving your admins the "m" flag by chance? They could be doing sm_rcon sm_slay playerName to slay people