よくもそんな

how dare you

→ 良く
phrase Rare #32,660
how dare you An indignant or accusatory expression, often followed by ことを or a verb. It can also mean “you've got some nerve” depending on context.
JA: よくもそんなことを言えたね!
EN: How dare you say such a thing!

俺に面と向かってよくもそんなこと言える

How dare you say something like that to my face.

よくもそんなこと

How dare you!

— 預言者 (2009)

私によくもそんな口のきき方ができるものだ

How dare you talk to me like that.