"I like you... but if you're ever going to hurt her you will die by my D'k tahg"

[K'legh]

It would be very nice if someone could translate this:

"I like you... but if you're ever going to hurt her you will die by my D'k tahg"

into proper Klingon.

I tried by myself but it's too hard since I just started learning Klingon.

[QoghtlhIH'u']

I'll give it a try:
"I like you... but if you're ever going to hurt her you will die by my D'k tahg"

chobel, 'ach Da'oy'moHchugh bIHegh DaqtaghwIjmo'

You please me, but if you cause him/her/it pain you die because of my D'ktagh
In Klingon there is no word for "her" or "him" so the meaning should be made clear by the context.

I welcome discommendations from aspiring and accomplished grammarians.

[tesseraktik]

I'll give it a try:
"I like you... but if you're ever going to hurt her you will die by my D'k tahg"

chobel, 'ach Da'oy'moHchugh bIHegh DaqtaghwIjmo'

You please me, but if you cause him/her/it pain you die because of my D'ktagh
In Klingon there is no word for "her" or "him" so the meaning should be made clear by the context.

I welcome discommendations from aspiring and accomplished grammarians.

majQa'! { Very good! }.  Some points, however:

vIparHa' is the most common translation of the phrase "I like you", but chobelmoH certainly works (note that it needs to be belmoH (to cause to be pleased), not just bel (to be pleased)).  I'd also consider vIparbe', meaning "I don't dislike you".

I'd recommend changing 'ach Da'oy'moHchugh ("but if you hurt him/her/it/them") to 'ach be'vetlh Da'oy'moHchugh ("but if you ever hurt that woman").

[QoghtlhIH'u']

Thanks Fraek, for your discommendations  

Now to include the concept "ever" as in "if you ever", that could be put as as soon as :
Da'oy'moHDI' as soon as you cause her/it pain
I don't dislike you would be:
qaparbe'

Which brings us to:

qaparbe', 'ach be'vetlh Da'oy'moHDI' bIHegh DaqtaghwIjmo'
I don't dislike you, but as soon as you hurt that woman you die because of my D'k tagh

I have a problem with the expression "that woman" because it reminds my of Bill Clinton: I never .... with that woman  

I can imagine saying this as a Klingon father:

qaparbe', 'ach puqbe'wI' Da'oy'moHDI' bIHegh DaqtaghwIjmo'
puqbe'wI' - my daughter

[tesseraktik]

He problem I see with using -DI' ("as soon as") is that it suggests that the person being addressed is expected to hurt her, while the goal of the threat is to dissuade him/her from doing so.

...and indeed, puqbe'wI' ("my daughter"), be'nalwI' ("my wife"), parmaqqaywI' ("my beloved"), chajwI' ("my close female friend" (only works if the speaker is female))...  ...it's all good!

I don't dislike you would be:
qaparbe'

HIvqa' veqlargh!  bIlughchu' { D'oh!  You're absolutely right! }

[K'legh]

Thank you all very much for so many and detailed translations!

You helped me a lot!

[QoghtlhIH'u']

problem I see with using -DI' ("as soon as") is that it suggests that the person being addressed is expected to hurt her, while the goal of the threat is to dissuade him/her from doing so.

Right, now I am stuck at figuring out how to best translate "if you ever ....."

So this is the closest we get:

qaparbe', 'ach be'vetlh Da'oy'moHchugh bIHegh DaqtaghwIjmo'
I don't dislike you, but if you hurt that woman you die by my D'k tagh