Synonyms for Go downhill:

• v.

  •come down (verb)
  • descend,
  • fall.
  •decline (verb)
  • disintegrate,
  • depreciate,
  • languish,
  • sink,
  • slide,
  • backslide,
  • decay,
  • droop,
  • fall off,
  • lapse,
  • diminish,
  • flag,
  • fade,
  • revert,
  • wane,
  • weaken,
  • drop,
  • ebb,
  • pine,
  • subside.
  •degenerate (verb)
  • go to pieces,
  • retrogress,
  • slip,
  • regress.
  •deteriorate (verb)
  • break,
  • moulder,
  • wear away,
  • spoil,
  • wilt,
  • collapse,
  • atrophy,
  • crumble,
  • degrade,
  • dilapidate,
  • putrefy,
  • wither,
  • tergiversate,
  • downgrade,
  • fall apart.
  •die (verb)
  • fizzle out,
  • peter out,
  • expire.
  •fail (verb)
  • founder,
  • fizzle,
  • go down,
  • go astray,
  • go wrong.

Antonyms for Go downhill:

• v.

  • come down
    boost, improve.
  • decline
    compliment, flourish, develop, grow, expand, laud, say yes, enlarge, raise, increase, rise, praise, build, extend, accept, advance, reach, win, enhance, ascend, progress, go up, strengthen.
  • degenerate
    aid, help.
  • deteriorate
    assist, fix, purify, join, put together, clean, approve, cleanse, clear, construct, heal, get better, mend, cure, elevate.
  • die
    forward, continue, appear, forge, bear, arrive, begin, prolong, be born, commence, live, start.
  • fail
    achieve, finish, procure, merit, prosper, capture, accomplish, complete, correct, deliver, gain, succeed, obtain, do well, earn.
  • rot
    combine, unite, upgrade, moralize.
  • sink
    fight, float, brave.
  • slump
    straighten.
  • worsen
    make happy, soothe, comfort.