I resigned and received my payout. Will this affect my UK visitors visa?

They really do not like unexplained larger deposits in your bank accounts when you apply for a UK visa. You need to combat two suspicions:

That you might be funds parking, ie have borrowed the money for a short period to artificially inflate your account balance and pretend you can afford your trip; but actually the money is not yours to spent at all.

That the money might come from some illegimate activities, or be otherwise a sign of economic affairs that are not entirely above book.

So you will definitely need to add the explanation for the payout (and ideally the accompanying documentation).

As jcaron pointed out in the comments, there is another way how your resignation will impact your application. Another important criterion is "ties to your home country", ie that you have positive reasons for going back after your trip to the UK. The fact that you have recently resigned your job will count against you here, and the question will come up whether you might have an incentive to illegally seek employment in the UK. How much of an issue this is will depend on your other circumstances, and probably the general employment situation in your home country. But be aware that right after the resignation from your previous job is probably the time where your application is the weakest.