Let's say that Starmer (the leader of the opposition who has already been investigated but found to have not broken any laws) is guilty of breaking the law (the same thing that Johnson has already been guilty of on one occasion so far)...
If people think that is worse than Boris Johnson, the Prime Minister who made the laws in the first place, consistently lied in Parliament about knowing that these parties took place, then lied in Parliament again to say that they did happen but no rules were broken and then refused to resign...
Well, that would just signify that they don't care about what Johnson did and it's, what do keep referring to... Playing politics.
If Starmer is ever found guilty of breaking any laws, at least you can be pretty sure that he would resign (and so he should).
The fact that you're even contemplating that these two are comparable when one of the two is literally the Prime Minister is beyond parody.
You're legendary balance needs a top-up on one side methinks.