@echo off

SET var=%1
SET last=some command to grab the last token of %var%
echo %last%
exit

For /F "Tokens=*" %%I in ('c:monitor.exe -C custom_performance_counter -t %1 -w 80 -c 90') Do Set COMMANDOUTPUT=%%I

Echo %COMMANDOUTPUT%
Set CURRENTVALUE=some command to grab the last token of %COMMANDOUTPUT%
Echo "The current value is %CURRENTVALUE%"

set var1=This is a String
for %%A in (%var1%) do set last=%%A

set xcmd=c:monitor.exe -C custom_performance_counter -t %1 -w 80 -c 90
for /f "tokens=*" %%I in ('%xcmd%') do for %%A in (%%~I) do set last=%%A
echo last=%last%

@echo off

set var1=This is a String
set var2=%var1%
set i=0

:loopprocess
for /F "tokens=1*" %%A in ( "%var1%" ) do (
  set /A i+=1
  set var1=%%B
  goto loopprocess )

echo The string contains %i% tokens.

for /F "tokens=%i%" %%G in ( "%var2%" ) do set last=%%G

echo %last%

pause

@echo off
call :get_last %~1
echo.%last%
goto :eof

rem get_last tokens...
:get_last
  set last=%1
  shift
  if [%1]==[] goto :eof
  goto get_last

@echo off
:l
set last=%1
shift
if [%1]==[] goto pl
goto l
:pl
echo %last%

@echo off

set var1=This is a String
REM token_string will be manipulated each loop
set token_string=%var1%

:find_last_loop
for /F "tokens=1*" %%A in ( "%token_string%" ) do (
  set last=%%A
  set token_string=%%B
  goto find_last_loop)

echo %last%

pause

for /F "tokens=1* delims=:" %%A in ( "%token_string%" ) do (

@ECHO OFF
SET var=This is a String
SET Token=0
SET last=
:Loop
SET /A Token+=1
FOR /F "tokens=%Token%" %%i IN ("%var%") DO SET last=%%i& GOTO Loop
ECHO The last token is: "%last%"
PAUSE > NUL