Fate/Grand Order has hundreds of servants to choose from and dozens of them are viable. 5 star servants are all excellent but some are just better than others. Ranking 5 star servants comes down to how versatile they are, how strong their skills and abilities are, as well as if they can work together with other units well.RELATED:
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5 star servants are the rarest in the game, as well as the most powerful. There're some lower rarity units that can compete with them, but generally, a 5 star servant is your best bet for tougher levels. Obtaining them is difficult especially if it's on a free to play account but with event banners and proper saint quartz management, it's possible to get a few.

S Tier

These servants are contenders for best unit in the game:
- Scathach Skadi introduced new tactics to Fate/Grand Order by making quick units a lot more effective. She can buff the strength of quick cards and also their critical damage. If that weren't enough, she can also increase NP gain through quick cards, dealing huge damage in the process. Her main weakness is that her HP and defense aren't so great, so she dies easily. This isn't a big issue though because she can kill enemies so quickly, she shouldn't need to be durable.
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Merlin's strength comes from his absurd team buffing abilities that make all fights a walk in the park. He improves the strengths of buster characters, produces critical stars passively, and has good damage to boot. As a support, his value is obvious in end game and mid game levels, no matter the challenge.
- Zhuge Liang is a pretty straightforward servant with the ability to boost NP gain for all allies. His other buffs have very high stats, so they're great for buffing a team during a rough battle. As an S tier servant, he should be included in almost every team if he's available.

A Tier

These servants are also extremely powerful and have value on a lot of teams. Players might have to build team structures around them to optimize them, but it isn't too difficult. Some specific A tiers to watch out for are:
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Beni-Enma , a new servant released with the 2021 new year's update, is a Swiss army knife of a saber unit. Her support abilities are great and varied, and her single target damage is more than decent. On top of those elements, she has a move to improve resistance to buff removals. This is a rare ability that should be taken advantage of. Her value also comes from her very niche damage boosts that she gets against enemies with certain alignments.
-As a standalone unit, Tamamo-no-mae is nothing too special. Her full potential is unlocked once she is placed on an arts based team. She can buff NP gain, buff NP damage, and heal the party. Pairing her with strong arts damage dealers makes for an unstoppable combo of a team.

B Tier

B tier servants have amazing strengths, but also their weaknesses are more prevalent than the servants listed above, so they need some -balance in team structure to make them work their best.
-A great example of this is
Xuanzang Sanzang . Her damage as a caster is unparalleled in the game currently, but she relies more on supports in order to achieve that damage. Her own skills don't buff her for long or provide much for the team in the long run. Issues like this are common among B tier servants but this doesn't mean they're weak by any means.

C Tier

Following the trend, C tier servants also have issues with solo viability, and rely on team-mates to carry the game plan forward. They range from extremely powerful to clumsily put together.  Players will definitely obtain a 5 star from an event banner sooner or later so it's important to learn how to use them when you get them.  Free to play accounts work pretty well in this game so there's no need to worry about getting specific 5 star units.RELATED: Genshin Impact: 10 Other Games With Insane Gacha Features
- Ereshkigal is a good example of the latter. Her abilities are all over the place which makes her a solid jack-of-all-trades unit, but that means she lacks true strength in any particular area. She has high HP and can survive for a long time, but since she lacks damage, that durability isn't very useful. Players are better off using a unit with higher attack and lower HP because dealing massive damage quickly is more effective than drawn out battles in Fate/Grand Order now.

D Tier

It's important to stress that even though these servants are low tier, they are still strong in their own ways. Not every player can pull S tier 5 stars, so it's important to understand what's in hand, rather than what isn't. These servants all have their own place in teams, it's up to the players to find those spots.RELATED: Fate/Grand Order: The Complete 3 Star Servant Tier List
Okita Souji is an interesting build of character because she is actually very powerful. She destroys cavalry units and can build NP for herself well. Souji also has other selfish abilities and AoE skills that help her deal more damage and build critical stars. Her biggest issue is that she is not very strong against a lot of the units players face in late game content. Her weaknesses dull her damage, making her a bad pick for a lot of more difficult stages.