back to back (?.)

• as one
• as one man
• at opposite extremes
• behind
• behind the scenes
• coactively
• coefficiently
• collectively
• combinedly
• communally
• concertedly
• concordantly
• concurrently
• conjointly
• contrariwise
• contrary
• cooperatingly
• cooperatively
• counter
• eyeball to eyeball
• face to face
• hand in glove
• hand in hand
• harmoniously
• in back of
• in chorus
• in concert with
• in the background
• in the rear
• in unison
• jointly
• just opposite
• nose to nose
• opposite
• poles apart
• shoulder to shoulder
• tandem
• together
• unanimously
• vis-a-vis
• with one voice