A negative effect can be:
Widowmaker's Poison from Venom Mine.
Reinhardt's Stun from Earthshatter.
Zenyatta's Orb of Discord.
Mei's Freeze from Bilzzard.
Ana's Sleep Dart.
Ana's Poison from Biotic Riffle.
Ana's Anti-Heal from Biotic Grenade.
Sombra's Hack.
Ashe's Burn Damage from Dynamite.
Junker Queen's Wound from melee attack, Jagged Blade, Carnage or Rampage.
Best scenario would be to keep an eye out for an ability that would affect your whole team, such as Ana's Biotic Grenade, Sombra's EMP (her Ultimate) or Junker Queen's Rampage (her Ultimate). If everyone gets hit with any one of these, try to cluster everyone on the team up and quickly use Kiriko's Protection Suzu, her RB ability on the whole team, including yourself.