So is Zero the Assassin a character class that should remain hidden and fight from far away? It certainly can be!
You can spec your character so that you're a high rate, damage per second (DPS) sniping build that can destroy enemies by blasting their critical areas fast and efficiently using the Sniping Skill Tree.
You can also say "eff that" and take up arms in the Bloodshed Skill Tree for the best Assassin Melee Build -- and when bundled with Cunning Skill Tree abilities, it becomes even stronger.
We aren't looking at a melee build though. We're looking at what's possibly the best Assassin solo build, which makes use of Zero's sniper rifle skills for massive damage. It also bundles in some health and shield skills for defensive purposes, making it like an Assassin Tank Build, but in general, they do not actually tank as well as other classes can (go to Salvador the Gunzerker for that).
This class build uses the Sniping Skill Tree up to tier 6 and then the Bloodshed Skill Tree up to tier 3. This build does not use the Cunning Skill Tree at all.
Best Assassin Class Skill Build
*** Decepti0n / Deception *** - Action Skill. Create a holographic decoy and vanish for a few seconds. The longer you are invisible the more Damage your next attack deals, but ending invisibility sooner causes your next Deception Cooldown to refresh faster.
Sniping Skill Tree
HeadSh0t / Headshot (5/5) - Increases Critical Hit Damage
Critical Hit Damage: +20%
Killer (5/5) - Kill Skill. Killing an enemy gives you bonus Critical Hit Damage and Reload Speed for a few seconds.
Critical Hit Damage: +50%
Reload Speed: +75%
Precisi0n / Precision (2/5) - Improves your Accuracy with all gun types.
0ne Sh0t 0ne Kill / One Shot One Kill (1/5) - The first shot fired from a fully loaded magazine causes Bonus Damage
Gun Damage: +12%
B0re / Bore (1/1) - Your shots pierce through enemies. If your shot hits an enemy after piercing an enemy, it cuases massive Bonus Damage. does not work with rockets and some special projectiles. Also, while Deception is active, your visor will highlight enemy crit locations.
Each additional target hit takes +100% Damage
Enemy crit spots highlighted while Deception is active
Vel0city / Velocity (5/5) - Increases Bullet Speed, Damage, and Critical Hit Damage with all guns.
Bullet Speed: +100%
Critical Hit Damage: +15%
Gun Damage: +10%
Kill C0nfirmed / Kill Confirmed (5/5) - Aiming Down the Sights with your gun grants you a bonus to Critical Hit Damage. The longer you aim down the sights, the greater the bonus.
Up to +40% Critical Hit Damage
At 0ne / One with the Gun (5/5) - Greatly improves your Accuracy with Sniper Rifles when shooting from the hip. Also increases your Reload Speed and Magazine Size with Sniper Rifles.
Sniper Hip-Shot Accuracy: +125%
Sniper Reload Speed: +50%
Sniper Magazine Size: +5
Critical Ascensi0n / Ascension (1/1) - Scoring a Critical Hit with a Sniper Rifle increases your Damage and Critical Hit Damage with Sniper Rifles. This effect can stack up to 999 times. Stacks slowly decay if you haven't scored a critical hit in awhile.
+6% Critical Hit Damage per stack
+5% Damage Per Stack
Bloodshed Skill Tree
Ir0n Hand / Iron Hand (5/5) - Increases your Melee Damage and your Maximum Health.
Melee Damage: +15%
Maximum Health: +15%
Grim (5/5) - Kill Skill. Killing an enemy causes your Shields to quickly regenerate and increases your Action Skill Cooldown Rate for a few seconds.
Regenerates +3.5% of your shield per second
Deception Cooldown Rate: +7.5%
F0ll0wthr0ugh / Followthrough (5/5) - Kill Skill. Killing an enemy increases your Movement Speed, Melee Damage, and Gun Damage for a few seconds.
Movement Speed: +40%
Gun Damage: +30%
Melee Damage: +40%
Assassin Strongest Class
The Assassin may very well be the strongest class out there. Play him well and you'll win every time. You can actually use a shotgun build for him too if you wish or a build more designed for close range combat, but that's entirely up to you.
With this build you'll want to get a nice rare, epic, or legendary sniper rifle with elemental damage to be at your best. You can also search for E-Tech Sniper Rifles or a Seraph Sniper Rifle too.
Be sure to get a nice class mod too, as you'll want it to help you further improve your skill set.