>>535808752
Go download OpenXCOM, pirate EW or WotC now, but I'll break it down for you since I'm feeling bored
>oldCOM
Melee wasn't a specialization, but melee weapons existed for you to stun ayys so you can capture them for anal probing. The sequel added more melee weapons that were one of the only reliable ways to kill a particularly tanky mid-lategame enemy. It was otherwise not worth it to use melee in most other cases.
>nuCOM
The capture mechanic returns, but the arc thrower was a tool, not a specialized melee weapon. The Enemy Within expansion introduced MEC troopers, soldiers nuggeted to fit into an exo suit, who can't use cover and had more HP to compensate, among other features. Such as the ability to use a rocket powered fist to sock ayys for a nice chunk of guaranteed damage with special kill animations for certain enemies.
>nuCOM 2
The Ranger class uses a blade as a secondary mainly to kill Sectoids, which have stronger powers but a melee weakness in this game, but it's also used to finish enemies outside LoS before you get the Run and Gun (can shoot after sprinting when activated) talent. In general, it was a risky attack that had a chance to miss against lategame enemies, offered no fallback moves and reveals more of the map, potentially triggering more enemies while leaving your Ranger exposed. Lategame, it had a niche with the Reaper talent, which let you chain melee kills with reduced damage after each kill. MECs were replaced by wholly robotic SPARKs, which also had a punch with no more rocket boost or special kill animations, lame.
The WotC expansion adde the Templar hero class, which had guaranteed damage and could either move or stand still and block one attack after attacking. This made Templars strong early on which could secure kills and get away easily, but they veer more towards a tank/support role later on.
In lategame, Rangers can get a boss' weapon after killing her, which does guaranteed damage and ignores armor.