Who are some of the groups or individuals that might kill a bill and keep it from becoming law?

Presidential vetoes, some people from senate or the house of representatives might kill a bill and keep it from becoming law.

Explanation:

When a bill gets vetoed by the president, then the bill goes back to the congress. The congress for getting the bill passed has to over ride the bill by getting at least a majority vote of two thirds.

But the over riding of the veto is very difficult because getting so many votes in majority is very tough. So if the over riding does not take place, the bill dies and does not become a law.