Script to raise a single window to the front
open only raises a single window:

do shell script "open -a Terminal"


Another way to raise a window is to set its index to 1 and then use AXRaise:

tell application "Terminal"
    set index of window 2 to 1
end tell
tell application "System Events" to tell process "Terminal"
    perform action "AXRaise" of window 1
end tell