Together with its undisputed economic relevance, complexity is undoubtedly one of the most salient features of the financial sector. Complexity bequeaths the adoption of a specific regulatory setting, as was the case with the creation of the Banking Union. In fact, deficient and inadequate regulation and supervision of the financial sector – largely due to an insufficient outside perception of risks incurred by financial institutions – coupled with a selective application of competition rules ranked highly amidst the reasons for the 2007–09 financial crisis. Consequently, it would seem that the rethinking of the overall regulatory framework should be complemented by a reflection on the role of antitrust enforcement in the financial sector. This chapter builds upon the latter premise and focuses on a specific type of antitrust intervention – the prohibition of abuse of dominance – and its interaction with the regulation and supervision of the financial (banking) sector. This reflection takes into account the recent evolution of competition rules in the financial sector in order to tentatively sketch a reappraisal of abuse regulation in the financial sector resorting to a notorious example: that of inter-change fees for card-based payment transactions.