That’s the one you need to do first. That’s where the highest impact and peak productivity lies, at least based on my experience.
Here are my three observations.
First, my willpower is strongest in the morning. Research suggests the same. Focusing on the most resented task first thing in the morning allows me to utilize my willpower at its peak. Other tasks in the morning would deplete my willpower and thus increase the risk of postponing the important task to the next day. (This is the same reason why I exercise in the morning. Have you ever skipped a planned evening workout because there was no willpower, energy, or time left?)
Second, there is a feeling of satisfaction from the beginning of the day. This satisfaction remains present throughout the whole day, no matter how the rest of the day evolves. (How do you feel during the day if you workout in the morning?)
Third, it leads to tremendous productivity boost via a compound effect. I have observed that resented tasks usually fall into the important not-due-soon quadrant, known as the holy grail of peak long-term productivity. Since resented tasks often relate to each other, results get built upon each other.
What would change if, for the upcoming month, the first task you do at work is the one you resent the most?