Some people are just there to ruin your happiness because they can't be themselves happy and don't even want others to be happy..
And if in case, you tell them that they are being 'toxic' then they will come up with tantrums and emotionally blackmail you and again ruin your happiness, by any possible mean. Such people have a mentality to always seek sadness and conflicts, and then make your life worse too, and you allow them, because they are important..
Hurtful but its true..
May god bless you!