There is no definitive answer to this question as different people have different opinions on what constitutes a "worst" Medicare Advantage plan. However, some factors that could make a Medicare Advantage plan less desirable include high premiums, high out-of-pocket costs, limited coverage, and poor customer service. The worst Medicare Advantage plan is often any plan that is misunderstood. The simple truth is that MA plans can be very confusing and they change annually. However, if you fully understand everything about these plans, are comfortable with their unexpected costs and fine print, then it's possible to avoid the pitfalls of the plan.