77七

@echo off
for /f "delims=" %%i in ('dir /b /a-d *.txt') do (
	cd.>"%%~ni_2%%~xi"
	for /f "useback delims=" %%a in ("%%i") do (
		findstr /xc:"%%a" "%%~ni_2%%~xi" 1>nul
		if errorlevel 1 (
			>>"%%~ni_2%%~xi" echo %%a
		)
	)
)
pause
复制代码

77七

@echo off
for /f "useback delims=" %%i in (`dir /b /a-d *.txt`) do (
	setlocal
	for /f "useback delims=" %%a in (`sort "%%i"^&echo #@#@#`) do (
		if not defined str1 (
			set "str1=%%a"
		) else (
			set "str2=%%a"
			setlocal enabledelayedexpansion
			if "!str1!" neq "!str2!" (
				>>"%%~ni_2%%~xi" echo !str1!
			)
			endlocal
			set "str1=%%a"
		)
	)
	endlocal
)
pause
复制代码

未过多测试，不知道行不行，文本排序后，将某一行与下一行比较，如果不等，则打印某一行。
排序会改变。