I wrote this awhile ago (not in a good place!) I'm thinking it might need some tweeking - is it too angry, too personal, too obscene?! Would value your thoughts please - but be warned the language is, shall we say a little risqué!

No Mercy

Fuck you! You selfish bastard!
You wanker, prick & cunt!
You think that I deserve this?
You're an ugly little runt!
Throughout our 14 years
Via control & manipulation
You've broken me, piece by piece
Well... It's time to change that situation
You think that you can fuck her
And keep me as a friend?
You think I'll take it lying down?
Believe me, this is the end
Our break up was hard enough
Without your little tart
I begged for you to give me time
Before you made a start
But you are a selfish bastard
And you're thinking with your cock
You claim to care about me
Well quite frankly that's a shock!
Your actions speak much louder
Than the lies you tell yourself
If you truly cared for me
You'd not have left me on the shelf
While you fuck your bimbo
I've been a broken wreck
But now I'm getting stronger
I hold all the cards in the deck
I hope you're happy with your choice
Because my door is firmly shut
So make the most of what you've got
With your plastic little slut!
I hope she has a razor blade
Hidden in her cunt
To cut your cock to ribbons
While you fuck her from the front
Or will you fuck her up the arse
I know that that's a passion
I don't s'pose it matters
You'll fuck her in a fashion
A fuck maybe behind a tree
Or on a beach in Wales
While she rakes your back to shreds
Without breaking her false nails
Her perfect perky boobs
Are pointing to the sky
They came with a price tag
You'll be glad you didn't buy
Remember not to get her wet
Her tan will run like tears
She really doesn't look
Her tender 32 years
Oh & don't forget your sunglasses
So you can gaze upon her smile
Those teeth so dazzling white
I bet that took awhile
You think I cost you money
I'm as natural as they come
You'll have to take a mortgage out
To pay for her new bum
Well fuck her good & hard my love
With the Botox you'll never know
If you give her any pleasure
She is false from head to toe

I hope you don't mind Vicky but this made me laugh loudly as it expresses so much anger and hate, in a really healthy way. You really capture the way anybody would feel like this in this situation. Anger is a very good therapy sometimes, and it doesn't get too personal here because you have not identified anyone or got lost in personal detail. Its just a good healthy rant.
Yes it is pretty explicit but you gave fair warning of that.
But I notice it shifts from attacking him to attacking her. Is your poetic persona letting him off too lightly? Also who is the poem directed at really? Have you shifted your perspective during the poem? It made me wonder whether the next poem would be about getting together again!
It makes me want to say to the person speaking in the poem "Don't dream of letting him anywhere near you again. People like that don't change, they just wheedle their way back in""
I find anger is a good antidote to depression. Sometimes depression is caused by holding anger in, because we fear to hurt others when it is such a strong feeling.
I think it might need a bit of an edit and a warning intro before reading it in an open mic.

Thanks Freda! Brilliant feedback! No I'm not offended that it made you laugh I think I often use humour when I'm angry! I use writing as a form of therapy & encourage others to do the same definitely agree keeping it in causes more pain & depression. I can safely assure you I am now separated from this person however at the time I wanted him back - fool!! It's interesting that you noticed the shift in the poem - it actually started out as two separate pieces then I decided to run it together - I wonder if it might work better separately? In so far as editing is there a particular bit you think needs it? I value your opinion - thanks again for taking the time to read & comment xx