How hard is it to beat a PR 2 competitor?

From a starting standpoint say a website with average back links etc, how hard would it be be to outrank them at google if they are PR2? Im looking into some new niches and found a "decent" one with a few pr2 toppers.

Not hard. PR is not the only indication of superiority in Googles results.

How long is a piece of string?

One way is searching for high ranking keyword phrases with a decent search for rate and applying these to multiple article sites.
Use Spyfu and enter the authority site domain to see what keyword phrases are being used, which in turn you can use.
Searching for relevant sites with a decent PR and asking the site owner about reciprocal linking.
Really there loads of ways, it just takes some hard graft.