What is THE BEST & STRONGEST Insect repellent on the market?

Any brand of repellent that contains at least 40% DEET is what you need. 40% DEET will give you several hours of protection. Nothing else works like DEET regardless of what the advertisements say. Higher concentrations last longer and repel better but can cause skin irritation. Test in a small area to be sure before hand. I use 40% in the Alaska bush country, known for billions of mosquitos, and it works great.