Monomaniac

The scientist was a monomaniac about finding a cure for cancer and worked on it tirelessly.

His father was a political monomaniac, and his dinner conversations always centered around politics.

The scientist was a monomaniac about her research on cancer treatments.

The child became monomaniac about getting the latest toy.

The monomaniac about conspiracy theories believed that the moon landing was faked.

The detective believed that the suspect was a monomaniac obsessed with revenge.