#Java, 101 98 62 42 bytes

()->{Runtime.getRuntime().exec("init 0");}

As @Snowman pointed out, the question didn't specify if a full program was needed, so this should still be acceptable.

Java, 101 98 62 42 bytes

()->{Runtime.getRuntime().exec("init 0");}

As @Snowman pointed out, the question didn't specify if a full program was needed, so this should still be acceptable.

#Java, 101 98 62 bytes

void f()throws Exception{Runtime.getRuntime().exec("init 0");}

As @Snowman pointed out, the question didn't specify if a full program was needed, so this should still be acceptable.

#Java, 101 98 62 42 bytes

()->{Runtime.getRuntime().exec("init 0");}

As @Snowman pointed out, the question didn't specify if a full program was needed, so this should still be acceptable.

#Java (versions 8+), 101 98 bytes Windows

interface C{static void main(String[]a)throws Exception{Runtime.getRuntime().exec("shutdown/s");}}

#Java, 101 98 62 bytes

void f()throws Exception{Runtime.getRuntime().exec("init 0");}

As @Snowman pointed out, the question didn't specify if a full program was needed, so this should still be acceptable.