てやる【～てやる】

The structure てやる has two main usages: doing something for someone (of lower status) and expressing strong determination or defiance.

Doing something for someone

やる is a rougher, more casual equivalent of あげる ("to give / to do for someone"). When attached to the て-form of a verb, **てやる** means "to do something for someone," but it is used when the recipient is of **equal or lower status**, such as children, animals, plants, or close friends in very casual speech.

Using てやる about someone of higher status or in polite situations sounds rude or condescending. In those cases, use てあげる or てさしあげる instead.

Expressing determination or defiance

てやる is also used to express a strong personal resolve – often translated as "I'm going to (do something)!" or "Just you wait, I'll…!" This usage carries a sense of defiance, ambition, or even revenge. The speaker is declaring their intent forcefully, often to themselves or to an adversary.

This usage is very casual and assertive. It is common in manga, anime, and everyday informal speech when expressing fighting spirit or frustration.

Polite form

The polite equivalent of てやる (in the "doing for someone" sense) is てやります, though in truly polite contexts, speakers will typically switch to てあげます instead.