What is Ruler's Strength/Weakness?

According to the wikia page for Ruler, they are resistant to the six regular classes, but deal regular damage to all.

All Six Regular classes (Saber, Archer, Lancer, Rider, Caster and Assassin) deal half damage against Ruler, but take regular damage.

It's worth noting that Moon Cancers, Avengers, and Berserkers are exceptions to the "take regular damage from" rule and one of them deals double damage to Rulers, but it appears to be the only class to do so.

Moon Cancers take double damage from Rulers and deal 50% less damage against them.

Avengers take half damage from Rulers and deal double damage against them.

Berserkers take double damage from Rulers and deal 50% extra damage against them.

Thus, a Ruler is strong against/resistant to all classes except Avengers, which is also the only class they are weak to. On the other hand, Rulers deal extra damage only to Berserkers and Moon Cancers.