fsharp-dotnet, 178 bytes

Result

AC

Duration

7367ms

Code [DL]

let f=stdin.ReadLine
let w=printfn"%s">>f
let T=f()
let t=T.IndexOf"T"
let mutable i=w T
while i.IndexOf"K"<0 do i<-w T
let k=i.IndexOf"K"
i<-w(i.[..k]+String.replicate(t-k)"K")

stdin

               T                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
         K                                        

stdout

               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
               T                                  
         KKKKKKK

stderr

The template "Console Application" was created successfully.

Processing post-creation actions...
Running 'dotnet restore' on /tmp/Proj/Proj.fsproj...
  Restoring packages for /tmp/Proj/Proj.fsproj...
  Generating MSBuild file /tmp/Proj/obj/Proj.fsproj.nuget.g.props.
  Generating MSBuild file /tmp/Proj/obj/Proj.fsproj.nuget.g.targets.
  Restore completed in 206.86 ms for /tmp/Proj/Proj.fsproj.

Restore succeeded.

strace