The contract, it should be noted, is horribly written. Undefined terms. Improper outlining. Certain topics dealt with through unconnected paragraphs. Paragraphs that start with one topic and thrown in some other topics. It's a nightmare. The lawyers involved in that contract should be disbarred.
The section you quote then goes on to say that a character is "in use" by Universal if it was significantly featured in advertising. I don't know how much Black Panther has appeared in ads as one of the Avengers.
Here's a better outlined version of that section with the parties in question updated:
After such 2 year period, UNIVERSAL PARENT COMPANY’s exclusive rights will be subject to “shrinkage” or “expansion” as follows:
1) If no action is taken by UNIVERSAL PARENT COMPANY, such exclusivity shall be limited as follows:
i. East of The Mississippi - any other theme park is limited to using characters not currently being used by UNIVERSAL PARENT COMPANY at the time such other license is granted.
[For purpose of this subsection and subsection iv, a character is “being used by UNIVERSAL PARENT COMPANY” if
(x) it or another character of the same “family"
. (e.g., any member of THE FANTASTIC FOUR, THE AVENGERS or villains associated with a hero being used)
is more than an incidental element of an attraction,
is presented as a costumed character, or
is more than an incidental element of the theming of a retail store or food facility; and,
(y) in addition, if such character or another character from the same “family” is an element in any UNIVERSAL PARENT COMPANY marketing during the previous year.
Any character who is only used as a costume character will not be considered to be “being used by UNIVERSAL PARENT COMPANY” unless it appears as more than an incidental element in UNIVERSAL PARENT COMPANY’s marketing.]