He can be a very good friend but a formidable foe.

But in the last few years they have come up against a most formidable foe: the economy.

She was a strong ally and would be a formidable foe.

The only way to deal with so formidable a foe was to gain the first advantage.

And all the brave men would be facing a more formidable foe.

Crime's formidable, relentless foe was taking over battle as his own!

He must have been up against a most formidable foe.

The father and the son have been my formidable foes over the generations.

That made him a less formidable foe, to Dirk's way of thinking.

"You yourself have stated that she is the most formidable foe we will ever face, sir."