Crimson Lotus: Phoenix Blade

Flame Lotus: Phoenix Sword (紅蓮鳳凰劍 Shira-ni-gata: 'Guren Hōō Ken): is a Fire Dragon Slayer Magic Spell.

Description
A Hidden Fire Form; Natsu ignites his entire body with the power of the Flame of Rebuke. He then charges towards the enemy and delivers a devastating punch he that blows up the enemy then proceeds to headbutt him. This is also described as The Ultimate Dragon Slayer Technique and the Dragon Slayer's Hidden Art, Sea Fire Style. This could be Natsu's strongest attack as not even Flame Lotus: Exploding Flame Blade was able to defeat Zero's strongest attack, though this may be because Exploding Flame Blade focuses on piercing penetration instead of mass destructive damage. This unstoppable and destructive attack was used to defeat Zero.