Look ! Everyone loves him ! 
On a more serious note. I know that almost every character is complained against every time it comes out, yet I never saw such a hate wave so far. My opinion ? Well, I didnāt encountered him at the moment, so I canāt really judge. But I had a bad feeling from the start when it was about spawnkilling. Looks like spawnkilling is not the issue though.
Here are some of the most interesting posts (in my opinion) I could find among the whole mass of salt and tears :
1 shots 5 mercs, leaves another 5 with less than 20 HP
no lunge, just long range on katana
stealth
Can survive a headshot by vasil with shield.
Can trigger a Proxy mine and martyrdom with shield and be at full HP.
Gets access to "arguably" the best SMG.
As fast as sawbones
I donāt even care whether heās OP or not, he is just frustrating to play against.
It feels really cheap to get one shot killed by an invisible guy. It feels even more cheap if you paid attention, saw him coming, unloaded your magazine into his cloak just to get one shot killed anyways because his cloak is a really powerful shield as well.
And there I thought Vassili was the most annoying thing Iād come across.
Any one who complains about his Katana is completely missing the mark. His peek advantage is ridiculous on top of having the Kek-10. Itās incredibly easy to time flanks after a wipe by waiting for the enemy team to respawn and then activate your cloak before they run past you. The amount of attention and awareness required to counter a Phantom is completely disproportionate to any amount of āfinesseā required to play him.
I think heād be more manageable if they reduced his health just a bit - just Nader/Bones level - and either weaken his stealth armor or remove the damage-gating effect it has.
There is no reason he should be so tanky with his stealth up, and āinstagibsā should still instagib him even if his stealth is active. If a Vassili gets a headshot on him, the Vassili should be rewarded. If the Phantomās dumb enough to run into an airstrike to try and get at the Skyhammer, the Phantom should not be rewarded. He should get blown sky high like everyone else.
Right now Phantomās too low risk for high reward.
Interesting entry on the wiki:
''Phantom is a merc first featured in close beta 1. The class had the highest Melee damage. The class during the first portion of CB1 was extremely over powered, later mid CB1 was nerfed too much, making him weak, and later was removed near the end of CB1 for two reasons.
He was too hard to balance
He didn't contribute to the objective''
Then why the fuck have they released him now. He clearly hasnāt become any easier to balance and as a result is broken as hell.
So many of you were ready to hate him before he even came out and the bias really shows. I really donāt think he is that OP. People just arenāt used to fighting him yet. I have played about an hour with him today and he is really fun but he is not a game changer unless he is going against unaware players. I lucked out and got a silver of his best loadout(kek10, katana, 20% melee damage and extended ability time). When you come face to face with someone if they just backpedal even the slower classes can just backpedal and avoid the swings. Swinging the sword is pretty slow and you have plenty of time to kill him before he can swing enough times to kill you. The only 1 shot kills are the low health mercs and they are so damn fast if they just keep moving you will never knife them. Plus they usually have shotguns which will tear you apart shield or no shield. Vasalli is also a direct counter to him because the recon probes make it so he cannot cloak when in their range. Itās the only merc that has a direct counter to another merc(so far). Phantom really only excels against unaware people and people standing still. I wouldnāt want to even pull a phantom when going against a competent team like you see in ranked or 10+. He is a pure pub stomper and nothing more.
EDIT : I also add the link to TotalBiscuitās Phantom video, just for fun.