What skills are needed to become a Senior UX Designer in the corporate world?

Sales skills. Yaa you read it right. I'm working as a senior in a design agency and believe me most of my efforts usually go to get buy in for my design decisions. I has to sell my designs regularly to my own colleagues and managers on daily basis. Apart from that another skill is ability to work under strict constraints like projects without research budget or unresponsive client.

Ability to connect business problems and strategies into your design. This way you can deliver better work and sell your design better.