ok, so first, before we get to how to play antagonist, we need to know what being the antagonist is all about.

the antagonist is a minion of the powerful uras beherit, made to be an extension of his will, which is to destroy the raiders, which is why you fight them and try to ruin their missions. as an antagonist, you need to be tactical and choose characters, weapons and cards fit for killing other players quickly and efficiently. you also need to choose your fights and tussles with the raiders in game based on how many enemies are around them, how many teammates are around them and what character they are playing as. its about selecting the time when they are distracted, weak or unable to counter you for some reason to pounce on them and eliminate them.

in short, being the antagonist is about killing other players as fast as possible.

when you enter the mission as antagonist, you first see the the character selection screen, where you can select a character. you can also see the raiders choosing their characters, so you can base your own character selection on the characters they choose, but they cant see that you (the antagonist) is in the mission until after they choose their characters. after they choose their characters, the timer at the top will jump back again to 10 seconds, leaving you a period to choose your character. you can also select and confirm your character before the raiders even choose their own, but its not recommended as your choice might be not suited.

once in the game, after the raiders spawn, you will also be able to spawn in one of some possible positions around the map which opposite the raider's spawn. to change between the positions press LMB or RMB to cycle to that position, and press space to spawn. when the mission has an antagonist in it, the enemy spawn (your allies as antagonist) will be reduced, and the difficulty will be slightly decreased to make it fair. objectives will also be mostly shorter/require less aleph.

this are the differences between you and the raiders.

• you get to choose when and where you respawn
  
• when you die, uras beherit will annoy you by saying in someway that you suck.
  
• when you die, you will not lose lives like the raiders, as uras beherit will respawn you himself.
  
• your respawn time is longer.
  
• the grunts and elites will not attack you, and you cannot attack them. use them to your advantage!
  
• you will sometimes get to hear uras beherit beautiful voice during cutscenes and area transitions.
  
• you will not be able to get ammo from any way other then melee killing raiders. manage your ammo carefully!
  
• you can only win by either killing all the raiders when the lives in the ship are depleted, or make them fail a timed objective (like in short-fused).
  
• you will lose if the raiders complete the mission.
  
• you can sometimes use aleph to heal some boss entities (the squid in weapon from the past, for example).

so here are some characters and weapon i think are good for playing antagonist. in my opinion.

Hans
default (preferably something else)
usu 21
heaven's bane
tarasque f-750
(good against fifth council, and basically everything that isnt alicia.)

Lycus
sh*t happens
pepper pot
(you should choose him if team is mostly tanks (kuzmann, konstantin), not if they have an alicia or hans. when you are choosing him, its mostly because he is more fun to play, most of the times hans will be better. nowdays he is kinda less broken, but still a lot of fun.)

Alicia
smoking daisy
rock & roll
the painkiller (with magazine upgrade)
(mostly good against hans, not as good against tanks.)

Konstantin
ogon shtorm
o.tsiklon uv9 (if you want a reliable gun more then a powerful one)
(you should choose him if team is high level, as he can dish out heavy punishment with reliable accuracy.)

Kuzmann
default
lichtbogen
(you should choose him if most players are low level, as they mostly wont know how to walk away from teammates when they are electrocuted, ending in the whole team dying pretty fast.)

Doldren
klt-13
bloody mary
patient boy
(you should choose doldren if you like high risk high reward gamestyle, as his ability lets you teleport behind your enemies and insta grapple them, giving you a quick kill, but as you are a local (native) character, your health is practically non existent and if you get chased down you will die pretty easily. overall i recommend him if you are more experienced and want to spice up your antagonist character selection.)

tip: never choose snipers, it will screw you in the long run. (unless you are a god with harec).
also dont choose slow, immobile characters without heavy punishment tools like valeria and aneska (and also ginebra if you cant aim).

this are general gameplay tips for playing as antagonist, they do not apply to a specific character.

• try attacking raiders which are low on health.
  
• try going for stealth grapples.
  
• dont charge into a group of 2 or more raiders, unless only 1 of them has higher then half health, or they are busy with elites.
  
• try attacking along with the elites, or staying near them if the raiders have to get aleph, as most people will not suspect/be able to fight you off with an elite helping you.
  
• you can grapple people while they are jumping, and they wont be able to counter you as jumping stops you from doing any actions for a while.
  
• most people will not be able to punch you quick enough when climbing ledges, so when they chase you, hop up on an object, turn around and grapple them for an easy kill!
  
• try attacking when covered by soldiers/elites.
  
• try to wound the raiders from a safe distance before going in.
  
• try not to let melee fights go on for too long, as most times their teammates will come along quickly to help them.
  
• do not get into a melee fight with more then 1 raider at a time.
  
• remember you can only get ammo from melee killing raiders, so dont waste all of it.
  
• beware from kuzmann, as he can attack you using the soldiers around you by electrocuting them.
  
• dont let the raiders melee kill you for aleph if the objective requires them getting aleph, sometimes go as far as to fall of a cliff or kill yourself to disperse the aleph if you cant protect yourself well enough.
  
• try targeting raiders with a high amount of aleph.
  
• its best to not go for melee unless the raider is downed or low or you are covered by a soldier/elite, sometimes they can surprise you with amazing melee skills.
  
• try changing the way you act in melee every time you get defeated in a melee fight, as this will throw off people.
  
• try utilizing the environment to kill the raiders, for example: turrets, slopes, corners, ledges, high ground, soldier spawn areas,and more.
  
• try baiting the raiders to follow you into a group of enemies, or behind corners for a surprise grapple.
  
• learn how most people act in melee (like some people get punched twice, then roll, some people just spam punch all the time without roll, other get punched once then roll, some punch punch grapple, things like that).
  
• try to stay undetected (aka keeping your aleph low), this will help you attack the raiders by surprise.
  
• try to always keep moving, changing positions and locations.
  
• go out there, get experience and witness strategies in the mission itself, as trial and error is a great way to learn.
  
• choose your spawn point and time carefully.
  
• if you have a ping over 800, or any amount that can disrupt your gameplay, your best bet is to just leave. dont worry if this will forfeit the match, because playing with high ping can be much more trouble then its worth. but do try to give the raiders some time (about 5 minutes) to switch host, since most chances that if you are experiencing lags, so are the raiders, and they will play about as bad as you will. you can always stay, but its not recommended in my opinion
  
• oh, and you can also just forget all that tactical crap and charge straight in like a madman, and sometimes the enemy players will be so surprised they wont be able to react. works especially well with CQC character like rak mayura and hive (more so rak, that healing zone be goooddddd).

as said, experience is the best teacher, so stop reading guides, and start searching for raiders to fight! (but dont be frustrated if you die at first, everyone has to start somewhere).