[RadioKid]

ましてセイントの中でも最強誇るフェニックスのクロス など演れん

In this video context, it is...

ましてセイントの中でも最強を誇るフェニックスのクロ スなどやれん。

"I will not give you the Phoenix Armor which boasts the strongest in Saint."

or

"I will not give you the Phoenix Armor which is said as the strongest in Saint."

(I don't fully understand the context even in Japanese.)

"最強を誇る" itself means "be proud of the strongest" when the subject　(indicated by "が") is human while it means "be said as the strongest" when the subject is not human being (because it would have no "pride").