According to the manual, the character can take a full action and execute 3 melee attacks and that is quite pretty crystal clear.

My question comes with characters armed with 2 weapons.
I've read and re-read the talet and I still don't quite understand a factor: "If the character has the Two-Weapon Wielder Talent and is wielding two melee weapons, the character gains the advantage of Lighting Attack with only one of the weapons, and a single attack with the other"

Does this means that he does 3 attack with the melee weapon and 1 with the secondary? (In total 4 attacks?)
I have a friend in the kill team who is an assault marine and in the current mission is equipped with a powerfist and a powersword, and I would like to know how to interpreter this talen, since he has it.

Also a quick question about attacks.
Unless is stated otherwise (like in the full auto or semi burst), melee attacks cannot be split among different enemies right?

Thanks in advance for the help!

It seems pretty clear to me. Three attacks with one weapon, one attack with the other, with appropriate penalties for two weapon wielding.

Decessor said:

I wanted to be sure :)

No problem. Happy gaming.

Decessor is correct, 3 with primary, 1 with the other when using TWW.

It is not disallowed to split your attacks amongst multiple enemies, though all of the enemies must be engaged (although assassin strike can complicate matters). I've always ruled a player must declare who he is attacking with which attacks before rolling any dice. If he doesn't declare he is smacking more than one character, he doesn't.

RAW: yup: 3 and 1.

However, we generally allow the player to make 2 attacks with each hand instead if they really want to. FOr the most part, seeing as Marines are ambidextrous and they can switch their primary hand whenever, we felt it was fine. Most people still generall will go 3 and 1 because unless both weapons are the same, one will almost always be preferred.

 3 and 1 is what was intended in the RAW.

And fantastic for even a basic chainsword/bolt pistol assault marine. Make sure he has the Flesh Render talent (extra damage die on tearing weapons) and you suddenly have 3 melee attacks, each with a very high damage outcome due to rolling 3d10 and picking the highest die, plus loads of strength bonus and some pen, all capped off with a bolt pistol shot (usually to the face as an execution/finishing move).

Macharias the Mendicant said:

I would agree with you, but it is your last sentence that points out why we are using a 2+2 rule. If you go 3+1 and the battle brother is armed with a chainswor and a power fist he would choose three strikes with the fist while still gains the advantege of the parry with the balanced chainsword. If you go 2+2 it kind of like he sacrifices one punch with the fist for the chance to parry with the sword. 

I'm not saying it is perfect, but it worked for us.