Can a legal heir to an estate overule, negate, or block in any way decisions made by the executor of the estate when distributing the assets of the estate?

Can a legal heir to an estate overule, negate, or block in any way decisions made by the executor of the estate when distributing the assets of the estate?

Maybe.

Was there a will? What state?

What is the specific issue you disagree with, and what does the will (if there is one) say about it?

The executor has to give out things according to the will or the laws of the state, if they are not doing that, the heir can sue or file a motion in probate court to have the judge decide if it is being done right. If not, they can order the executor to do it correctly, or even pay back if they did something illegal.