Friso94
26th Sep 2018
Avengers: Infinity War (2018)
Answer: While it's purely speculation, here are few ideas: 1. He didn't think he needed to. He now possesses the most powerful weapon in the universe and thought hitting Thanos in the chest would be enough. 2. He may have aimed for the head, but Thanos was trying to repel the axe, which caused the aim to be off. 3. He wanted Thanos to die slowly so that he could deliver his "I told you..." line.
Answer: Didn't think he had to.