You don't even need to produce an AGI for this kind of intelligence to be frightening.

At some point, a military is going to develop autonomous weapons that are vastly superior to human beings on the battle field, with no risk of losing human lives, and there is going to be a blitzkrieg sort of situation as the relative power of nations shifts dramatically.

If we have two such countries we could have massive drone and cyberwars being fought faster than people even can comprehend what's happening.

Right now most countries insist on maintaining human control over the machinery of death. But that will only last for as long as autonomous death machines don't dominate the battlefield.

It's a fun challenge right now to build a machine that can win in Starcraft, but it's really a hop skip and a jump from there to winning actual wars.