一いっ線せんを越こえる

Meanings

1

ichidan verb, expression

cross the line; go too far

idiomatic expression

Idiomatic expression for overstepping a moral, social, or personal boundary. Often used when someone does something unacceptable or violates a norm.

あの

政せい

治じ

家か

の

発はつ

言げん

は

一いっ

線せん

を

越こ

え

た

と

思おも

う

。

I think that politician's remark went too far.

一いっ線せんを越こえる
Standard kanji spelling; 越える is the more common kanji for crossing a boundary.
一いっ線せんを超こえる
Alternate kanji spelling; 超える emphasizes exceeding or going beyond a limit.

度どを越こす
Also means 'to go too far,' but focuses on exceeding a proper degree or limit in behavior or quantity, without the strong boundary-crossing image of 一線を越える.
行いき過すぎる
Means 'to go too far' in a more general sense, often for actions or remarks that are excessive, but lacks the idiomatic boundary metaphor.

From 一線 (a line, a boundary) + を + 越える (to cross over). The phrase metaphorically refers to crossing a figurative line that should not be crossed.