Which of the seven events do you think had the most devastating effect on the relationship between Great Britain and the British colonies?

The correct answer to this open question is the following.

Although your question is incomplete because you forgot to include the events to answer it, we can comment on the following.

One of the events that had the most devastating effect on the relationship between Great Britain and the British colonies was the heavy and constant taxation.

Yes, the  English monarchy imposed many taxations on the colonists that suffered to pay them. We are talking about taxation such as the Stamp Act, the Navigation Acts, or the Tea Act.

These taxations infuriated the colonies. The worst part was that they had to pay taxes but had no voice or representation in the British Parliament. Taxation was one of the most important reasons that initiated the American Revolutionary War in which the US fought the British troops to gain independence.

the steam engine.

the locomotive.

the telephone.

the telegraph.

the internal combustion engine.

the rifle.

ironclad ships.

electricity/light bulb.