9S is a free unit obtainable during the NieR: Automata Collaboration event. He is a defensive support oriented unit that can reduce enemy's stats, provides buffs to help with survivability, and can still deal decent damage as well. His elemental and attack type resistances are pretty good too, but -10% magic resist can be an issue against certain enemies/meta. He is also a machine type unit instead of human, so human killers won't work on him.
His new and unique YoRHa job comes with some good range on most of his skills. 2 buffs that can increase DEF + SPR (Shield Deployment), and ATK + ACC (Assault Field), then a debuffing attack on an enemy to reduce ATK + MAG (Hacking). YoRHa subjob can reduce DEF and AGI (Target Scan), which is also very good, and makes it so he can debuff most relevant stats on an enemy, but it doesn't deal any damage.
However, his Nightblade subjob is actually very strong since it comes with the important skills. Double Resist adds on to his already good pierce resist from 20% to 45% before VC or any equipment, and his missile resist from 5% to 30%. He then also has AP Drain, and Drain Rush for high chaining potential. Unfortunately, all Nightblade job attacks are slash type (but he uses a spear weapon), and he also does not have any hate increasing ability to capitalize on his good defenses.
Meanwhile, his Viking subjob is only worth considering if you need Killing Axe in certain situations.
His EX upgrade is quite good as well. AGI reduction on Cyclonic Spearshot is nice since it's a ranged area attack. His job lvl 25 skill, Linear Spearshot+, reduces enemy's pierce resistance, which can considerably increase 9S' damage, or your team if you're using mono pierce, and it's not expensive AP-wise with good range too.
Raises own DEF Piercing Rate, then deals Lightning Dmg (L) to target.
Seems like that could be a strong team, especially as the earth meta isn't the greatest. Problem is no hate generation for 9S, and Landu and Freddie are usually glass cannon build. 9S would likely be the toughest out of the 3 of them, even with Freddie's upcoming EX.
Will be an interesting team, not doubt. I pulled hard for 2B and missed, so scrambling to get enough shards to fully EX 9S.