Head-to-head (adverb)

1. In a direct confrontation or competition between two individuals or groups.
2. Directly and uncompromisingly, with no attempt to hide or conceal.

Origin:

This phrase is believed to have originated in the mid-19th century, as a reference to the physical positioning of two horses or other animals facing each other in a race or competition. it has since been extended to refer to any competition or confrontation between two individuals or groups.

Examples:

1. The two companies competed head-to-head for market share.
2. The two candidates debated head-to-head on national television.
3. The tennis players faced off head-to-head in the tournament final.
4. The rival coaches met head-to-head to decide the outcome of the game.
5. The armies battled head-to-head in the final showdown.