Perhaps it will help you if:

- you accept that people act out of ignorance

- you accept that you have also done wrong to others in the past

- you notice that you will not(hopefully) do revenge action

And you are already noticing that carrying around resentment towards others is poison for your mind.

It's easy to love people that are kind. But isn't it so that unkind people needs most love because of what they are doing to themselves?

I don’t know what your Metta practice looks like but it sounds like you need to offer yourself more of it. Losing your equanimity and experiencing those emotions you’re describing is very human and I encourage you to be compassionate and forgiving towards yourself. Our practices doesn’t make us perfect beings but offers us tools to be ok with our imperfections. 

Loving kindness does not mean you have to like or do favors for the other person. It’s enough to just make sure hatred and delusion dont grow inside of you. Keep yourself safe if youre going to be around people who you know are unsafe

By cultivating compassion and loving kindness towards oneself, making that strong and powerful. Then towards those that are liked, making that strong and powerful. Then towards those that are neutral, then those that are slightly disliked. Then those that are toxic. Once you have all the power from the previous practices, you use that power and apply it to the people that are toxic, etc. with that amount of power being used, it becomes not that difficult.

Start with mindfulness and meditation. That will help you see the whole process more clearly. Actually being compassionate is not something we can turn on or off. It depends on letting go of egoic clinging. Don't try to force it by conceptualizing. That will result in "performative enlightenment".

Also, you might think about why you use the word "toxic". People are not toxic. There are people who push your buttons and therefore you don't like them. The toxin is your own. A core aspect of Buddhist practice is in recognizing that we need to work with our own minds. Samsara is not "out there".

The more you practice just being aware of your thoughts and emotions moment to moment, the more you'll be able to recognize when you are getting caught up in anger. It takes time and lots and lots of practice. Don't expect perfection. Be kind to yourself.

Separate the actions of such a person from the actual person. Try to remember that that person is also suffering in samsara no matter what the actions they performed were. This is extremely difficult. If you don't need to engage with these people, then don't do so. There's no need.

Don't expect transformation in yourself overnight and don't beat yourself up because you still have those negative feelings. It's a lot of work that begins with yourself and having compassion for yourself. As we progress we can start to extend it to friends and family with whom we don't have problems of any great import. Eventually we can move it out to those with whom we have problems and so on.

Every time we slip up, forgive yourself and return to your practice again and again and again. Because we all slip up and make errors. It's part of samsara.

I practice on the spot tonglen. I practice it a lot, often with easier peoples. People who are just annoying. So when more difficult people come along it is easier. Develop the habit. Of cutting negative thoughts. You can try adding positive thoughts and understanding what made that person the way they are .

Couple of thoughts. First, thanissaro bhikkhu puts it well —

To make this a heart-changing practice, ask yourself—when you’re secure in your goodwill for yourself—if there’s anyone for whom you can’t sincerely spread thoughts of goodwill. If a particular person comes to mind, ask yourself: “What would be gained by this person’s suffering?” Most of the cruelty in the world comes from people who are suffering and fearful. Only rarely do people who’ve been acting unskillfully react skillfully to their suffering and change their ways. All too often they do just the opposite: They hunger to make others suffer even more. So the world would be a better place if we could all simply follow the path to true happiness by being generous and virtuous, and by training the mind. With these thoughts in mind, see if you can express goodwill for this sort of person: “May you learn the error of your ways, learn the way to true happiness, and look after yourself with ease.” In expressing this thought, you’re not necessarily wishing to love or have continued relations with this person. You’re simply making the determination not to seek revenge against those who have acted harmfully, or those whom you have harmed. This is a gift both to yourself and to those around you.

Other advice comes from Ajahn Sona / Brahm. He likens metta to a fire you start. Start with the easy folks (a loved one, a cat, etc.) to get the "fire" of metta going. Only once the fire is raging do you throw on "wet logs" (difficult people).

Many people are motivated by control or power, we cannot help them. There will be something that will wake them up and changes their motivation.

A sentence I heard in a meeting a long time ago that stuck with me was that ….”Resentment is like drinking poison and expecting the other party to get sick from it”

This translates across so many different life challenges.

Whenever people do or say something I find offensive or rude, I remember it is their action not mine. No control available.

As I’ve gotten older I’ve also kept better boundaries. That’s more practical advice I can give.

You’re doing a great job by even asking these questions. Very good. 👍 Happy new year from Khao Lak!

Becoming trauma informed helped me.

Stop your judgement of thinking there are toxic people. Allow them into your heart but out of your life.

“May I love all beings and realize which beings I have no business with.”

And set your boundaries.

If you can get to the point where you can wish them the wisdom and lightness so they're no longer toxic, you're already there

Nobody wants to be toxic. Toxic people only express what's inside them, and the process of accumulating those toxic feelings/thoughts usually involve a LOT of suffering