if you had to fight an alicorn

[The Wandering Magus]

I still say words are the most powerful weapon break any stallion or mare's will with naught but voice, ideas.  break them utterly, until they cannot even stand their own selves, bowing willingly to you without ever having to so much as lift a finger.  Preferably in three sentences or less.

[Asterian Starfall]

Scenarios:

Spoiler: Diplomatic Relations • show

Simply defuse the situation best I can with words, which - not to be a narcissist - shouldn't be too hard, given my psychological insight and rakish charm.

Now assuming I have no choice but to fight:

Spoiler: Battle Tactics • show

Friendly Duel:
Phase 1: Build a small fire/ice wall in front of me.
Phase 2: Peer out from behind the wall and throw a snowball at them. Repeat until they approach the wall.
Phase 3: Let the wall disintegrate and tackle them; hold up an ice spear to them, then shake hooves.
Life-or-Death Situation:
Phase 1: Freeze their hooves and wings to weigh them down so they can't fly or attack in melee combat.
Phase 2: Dodge their attacks best I can while maintaining my distance, trying to wait for an opening.
Phase 3: Take advantage of the opening and launch a fireball at them.
Phase 4: While they're recovering, use my knowledge of hoof-to-hoof combat and chip away at them until I can't anymore. Repeat phases 2-4.
Phase 5: When either exhausted or nearing victory, vanish in a cloud of fog.

[Azure]

Summon a giant wall.
Bang boom done.

[narwhaliagames]

I would just use my robotic oc's because robots cant die

[Guardian Dreamer]

I will just stare, stare, stare!

[The Wandering Magus]

I will just stare, stare, stare!

[Applestack]

Alicorns are like Boss enemies in MMO games. Nopony can take on an alicorn in a full frontal battle alone. Phenomenal teamwork and excellent strategy is a must and you'll need to wear the alicorn down while making sure you and your comrades survive. Always the tanker/guardian/protector type, I would be an earth pony because earth ponies are the toughest and have great endurance. I would 'tank' while the others attack.

[GoldenTerrabyte]

Well, I'd just use words.
"This is Equestria. Why are we fighting like this anyway? Isn't this a peaceful kingdom?"
"...Good point."

[The Wandering Magus]

you know... just become a Draconequus and snap your claw.  tada, the alicorn no longer exists, or turns into cotton candy.  Then summon a bunch of starving rabbits and... bon appetite.

[Flamestriker]

I would never get into the fight to start off with normally, however, if I had no choice, I'd use my unicorn magic that my unicorn has. Either that, or bring Pinkie Pie along. 

[Teal Turken]

"No thanks. I'll just die, okay?"

[Guardian Dreamer]

I will just stare, stare, stare!

Well, I'd just use words.
"This is Equestria. Why are we fighting like this anyway? Isn't this a peaceful kingdom?"
"...Good point."

I know, I'm just kidding. Wait, this is not thread game... DERP.

[The Wandering Magus]

Calmly press the pause button, enter edit mode, remove all appendages and non-life-critical organs, and unpause.  Watch bemusedly as the writhing thing on the ground screams without screaming.  Offer said writhing pile of pitiful flesh a deal: if it follows the script from this point forward, forever, it shall not have to suffer this pain and humiliation again.  Replace its muzzle and vocal chords so it can speak.

[TwilightNight]

I would be smart and/or cowardly and just run. if they can make the sun and moon rise and fall, turn living beings to stone, and send other beings to the moon, I'd just run.

[GoldenTerrabyte]

Just face as an earth pony. Alicorns can't help but show off their wings and horn to an earth pony. That alicorn'll be to busy to fight! Earth pony wins!