Worst things you can do to the signs...

Aries: undermine them

Taurus: tell them they're wrong

Gemini: be too clingy/needy with them

Cancer: doubt their loyalty

Leo: one up them

Virgo: take them for granted

Libra: pick a fight with them

Scorpio: lie to them

Sagittarius: give them an ultimatum

Capricorn: play games with them

Aquarius: try to sympathise with them

Pisces: invalidate them