This is really hard to make a good case for because there are so many variables involved, for example;

• Are we discussing hyothetical scenarios here or only the armies as they actually preformed in the field?

Can we measure Sweden against the British army even though the two never actually met on the field?

• Are we taking into account such factors as ability to sustain a war for an extended period of time or only measuring pure punching power of a specific army in the field?

As an example, the Swedish army was, due in large part to Swedens relatively small population and industrial base, hard pressed to replace losses both in terms of manpower and equipment.

• How do we determine "powerful"? Is the power of an army determined by its number of men, cannon and horses, the quality of those, the leadership, all of the previous? Perhaps power should be determined by only by actual preformace on the field or indeed by the outcome of the battles an army fought and their long term strategic gains or losses?

The Swedish army might for example be said to have been very powerful during the expansive phase of the Swedish empire but ultimately it was defeated by the Russian army which, by several of the factors listed above, might arguably be said to be the weaker army.

I am aware that this is not an answer to the question asked but since the term "most powerful" can be defined in so many different ways I felt that it might be relevant to determine by which factors we measure the power of an army before we get into a discussion of this nature.