I could provide him with little else-I might have, once, been a formidable ally, but no longer.

And when he wasn't predictable, he was quite a formidable ally- or foe.

Certainly, there was no denying that the Borg would make a formidable ally against the Alliance.

We could not face him and his armies alone, but we would make formidable allies.

And you would make a formidable ally, if I decided to take you into my confidence.

Even Democrats describe him as a formidable ally - when they are not at odds with him.

I'll admit, in light of my previous underestimation of your capabilities, that you'd make a formidable ally.

Such were the formidable allies that ranged themselves against Aeneas.

Potentially, it is a formidable ally or rival.

He had won himself a formidable ally.