Amakusa Shirou is an offense-oriented Ruler Servant, whose greatest boon is the buff removal built-in to his Noble Phantasm - which is rather spammable thanks to his second skill. Being a Ruler, he also has high survivability in most situations. Against Servants - who are often the harder enemies -, his third skill’s stun can be highly useful as well.
His greatest weakness, however, is that his damage potential is somewhat questionable compared to other Buster-oriented Servants. While his upgrades largely fixes it in regards to NP damage, he possesses no critical absorption or damage increase skills, thereby limiting his damage potential.
Pros
High survival as he takes half damage from most enemies
Buff removal is highly useful in harder stages
Third skill has a stun against Servants
Cons
Mediocre damage
No utility aside from buff removal and the situational stun
Strategies & Tips
It is recommended to only use Amakusa in stages where he is necessary - while he excels in harder fights, generally speaking, there are probably more suitable alternatives for normal ones. He is best paired with allies who can enhance his damage. In battle, his second skill should be used as early as possible, while his stun is better reserved for crucial turns. Additionally, while his NP is usually used to start a Brave chain, it can also be used to safeguard the team when the opponent has threatening buffs.
Noble Phantasm
Twin Arm - Big Crunch is Amakusa’s primary way of dealing damage, and its buff-removing effect is the defining point of his kit. However, it is notorious for its low damage, especially before Amakusa’s upgrades. After the upgrades, its damage is on an acceptable level, although it still leans on the weaker side. This NP also inflicts a critical chance debuff, which is highly useful in harder quests.
With his buffs, critical generation, and survival features, Merlin is Amakusa’s best support choice. Their critical chance debuffs also greatly mitigate Merlin’s primary weakness - that is, his lack of defense buff. Do note, however, that Amakusa may need help in gaining/gathering stars to ensure that Merlin’s third skill does not come to waste.
Nightingale’s heals are more significant when used on Amakusa, who is a Ruler. Her NP also provides a way to defend against opposing NPs, as Amakusa lacks any function of the sort. Her low star weight also helps Amakusa in gathering stars.
Both being Rulers, using Jeanne alongside Amakusa means that the team will be very tanky. In addition, the pairing also covers a wide variety of situations, as the team would then possess team-wide Invulnerability and party-wide debuff removal from Luminosite Eternelle, as well as buff removal from Twin Arm - Big Crunch. Their Stun also go together, able to stall enemies for as long as two turns. However, that as they have similar critical star weights, it means that Amakusa will experience trouble in gathering stars without the aid of a critical absorption CE.
As with most other NP-oriented damage dealers, this CE type is arguably the best for Amakusa, especially due to NP buffs being multiplied against other, more common buff types.
With his lack of an absorption skill, performing critical hits reliably may be somewhat of a problem, especially if he is brought alongside Servants with similar star weight. These CEs aim to fix that problem, ensuring he will be able to gather critical stars consistently.
Boosts Amakusa’s Buster cards’ performance. This CE type is best used if Amakusa is brought along with Caster allies, as he would be able to perform more critical hits in these compositions.
Generating critical stars for three turns, Revelation helps Amakusa in performing critical hits, especially considering his lack of critical absorption skill. Unfortunately, the amount of stars this skill produces is not that significant, especially at lower levels.
Baptism Rite B+
Charges Amakusa’s own NP gauge every turn for 5 turns. It also decreases the NP charge of an Undead or Demon enemy by one, but due to its situational nature, this skill is mostly used for the NP charging effect. Due to this skill’s long cooldown, the leveling of this skill is important if it is to be used more than once.
God’s Resolution C / God’s Resolution (False) C++
This skill has a high chance to Stun an enemy Servant. While fairly situational, it is still a great asset in harder battles. After its upgrade, this skill also grants a 3-turn Buster buff for Amakusa, greatly increasing its usefulness.
Revelation A
Available from the start Gain C. Stars each turn for yourself (3 turns)
Lvl
Stars +
Cooldown
1
3
8
2
4
8
3
5
8
4
5
8
5
6
8
6
6
7
7
7
7
8
8
7
9
8
7
10
9
6
Baptism Rite B+
Unlocks after 1st Ascension Decrease a single [Undead or Demon] enemy's NP Gauge Increase your NP Gauge (5 turns)
Lvl
NP +
Cooldown
1
10%
12
2
11%
12
3
12%
12
4
13%
12
5
14%
12
6
15%
11
7
16%
11
8
17%
11
9
18%
11
10
20%
10
God's Resolution C
Unlocks after 3rd Ascension Chance to immobilize one enemy (1 turn)
Lvl
Stun Chance
Cooldown
1
50%
8
2
55%
8
3
60%
8
4
65%
8
5
70%
8
6
75%
7
7
80%
7
8
85%
7
9
90%
7
10
100%
6
God's Resolution (False) C++
Upgrades after the Strengthening Quest Chance to immobilize one enemy (1 turn) Increase your Buster Card effectiveness
Lvl
Stun Chance
Buster +
Cooldown
1
50%
20%
8
2
55%
21%
8
3
60%
22%
8
4
65%
23%
8
5
70%
24%
8
6
75%
25%
7
7
80%
26%
7
8
85%
27%
7
9
90%
28%
7
10
100%
30%
6
Class Skills
Magic Resistance A Increase your Debuff Resist by 20%
Command Cards
Card
Quick
Arts
Buster
Extra
Hit-Count
3
2
1
6
Shirou’s command cards performance is pretty decent with slightly higher NP gain and star generation compared to Jeanne of the same Ruler class while being able to deal six hits with his Extra card.