at daggers drawn

be at daggers drawn AND at daggers points (be angry and ready to fight or argue with each other) — на ножах, в состоянии (непримиримой) вражды; враждовать

Example 1: Do you know why Michelle and Peter are at daggers drawn again? - Oh well, they are always at war. If you take either's side you risk being on bad terms with the other one.

Example 2: Local residents are at daggers drawn with the council over rubbish collection. (often + over)

Example 3: The two countries have several times been at daggers drawn over the future of the island. (CIDI)

also
at loggerheads
[at each other's throats]
at odds/at war
on bad terms