Infinity war’s thanos proves cgi supervillains are a terrible idea , ideas?

Infinity War’s Thanos proves CGI supervillains are a terrible idea , ideas?

The correct answer is:
 Infinity War’s Thanos proves CGI supervillains are a terrible idea.

We used idea since before the word terrible, there is "a" word which signifies that it is singular and CGI supervillains is a singular word thus making the "idea" also a singular.

The virginia plan was a proposal by virginia delegates for a bicameral legislative branch. the albany plan of union was a plan to create a unified government for the thirteen colonies.