Key board commands

There is not. Why exactly would you want such a command?

I love to do it in Command and Conquer. It's just fun to make up your own storyline sometimes - say that your fleet fights a battle and is completely destroyed except for one capital ship. But you, being the evil galactic ruler that you are, do not allow retreat. It is cowardice, and cowardice in your crew means death. You tell all of your other ships at your homeworld to attack the badly beaten capital ship as soon as he arrives.

They quickly eliminate the cravens. Honor and order is restored for your empire is restored as you have preserved the integrity of your fleet.

I love doing this in other games, why not in Sins?

I don't know if thins is ry8472's reasoning, but I would love to see such a small feature as this implemented  in Sins - just a "Force Attack" button. But at this stage it might be too late. And it is really minor.

Make a mod with martyrdom or red button on every ship....problem solved....

Ah, but you see, it is different to self-destruct than to command your entire fleet to destroy one of their fellow ships. Self-destructing, it, well, just doesn't have the same sick joy to it. It doesn't make me feel EVIL.

But what if there was an ability that turned the selected ship neutral, so that your ships could attack it, that would be ideal. Because not only would I get to tell my ships to fire on another one of my spacecraft, but that spacecraft would quite literally be "rogue" and would fire back.

But that does belong in a mod, I guess. Could it be done?

Not really. You can really only convert a ship to the owner of the ability. It is annoying that you can not even revert a captured ship to the original owner without some fancy ability work. I won't say it is impossible, but it would be a real pain to do and wouldn't be as simple as the button we're discussing.

You could make an ability for a command ship, as ability slots on ships are not that readily available, to do the opposite of heal. Attach the weapon effect to an ability point on the mesh and boom, your command ship drops the shields and fires a couple torpedoes into the bridge. I also would not recommend auto cast for that one, although, the ensuing havoc would be hilarious to watch.

Mephistopheles  

that is my reason exactly. 

i to "got addicted to the function in Command and Conquer and other games" and it's a bit disappointing that sins don't have such a command.

That is an awesome idea. Just to have one "Executioner Ship" (maybe the titan?) that would eviscerate all unfaithful in your empire. Hmmm... The ensuing havoc would be hilarious. Maybe I'll make myself my first mod one of these days.

I can just imagine at the end of the match, when the Victory screen comes up and I press "Keep Playing", then take every ship in my fleet and activate the ability (assuming every ship has an ability slot open), then have a last-man-standing final battle among my own ships. Positively awesome. A REAL rebellion in Rebellion!

It would be a fairly easy mod to make if it was to be your 1st.

GameInfo folder with a new ability and buff file
entity.manifest listing new ability and buff, change count

String folder with English.str and add the button label and desc, change count 

Add the different version of each button to an empty space in the existing Buttons_Research_xxx.tga textures and put them in the Textures folder

Add the new ability to the chosen ships available ability slot.

Lots of people here to help you.

EDIT: Forgot, the 4 buttons 'states' need to be added to a brush file located in the Window folder which point to the new button textures. Change Count. Reference_Files_Dip_v1.37/Window/HUDIcon-Ability.brushes

brush
	name "HUDICON_ABILITY_TECHORBITALCANNON"
	content "States"
	Disabled
		fileName "Buttons_Research_Disabled"
		pixelBox [ 5 , 216 , 47 , 33 ]
	Pressed
		fileName "Buttons_Research_Pressed"
		pixelBox [ 5 , 216 , 47 , 33 ]
	CursorOver
		fileName "Buttons_Research_CursorOver"
		pixelBox [ 5 , 216 , 47 , 33 ]
	Focused
		fileName "Buttons_Research_Normal"
		pixelBox [ 5 , 216 , 47 , 33 ]
	Normal
		fileName "Buttons_Research_Normal"
		pixelBox [ 5 , 216 , 47 , 33 ]

Mephistopheles