Star Ocean: Till The End Of Time

In order to reach the Dirna and Solon fight, you need to reach Rank #1 from playing the Ranking Battle's at the Battle Arena. How the Ranking Battle works is that you must register a Team Name first (this doesn't really matter, but slightly raises certain party member's affection for you), after registering your team name, you will be placed at Rank 50 and must work to get to Rank 1. You can fight up to 4 Ranks ahead of you, and you will want to do that in order to make this process go a bit faster. The first 30 or so fights will go well; it's only when you reach around Rank 20 when the difficulty will start to pick up. Because you'll only be fighting one battle at a time with your team, feel free to heal after each fight as needed. When you defeat the Rank 1 team and claim the spot for yourself, you will be challenged by the reigning champions Dirna and Solon themselves the next time you talk to the Battle Arena receptionist. This is where thing's will start to get really difficult.

Dirna Solomon
HP: 3,000,000
MP: 500,000
Level: 174

Solon Solute
HP: 500,000
MP: 50,000
Level: 174

Given how much health Dirna has, you'll want to keep her stunned by combos for as long as you can while you or another party member focuses on Solon. Dirna has really powerful spells such as Explosion and Arcane Stars that can destroy your party's health really quickly if you aren't properly leveled. Despite the level of both Dirna and Solon, you can be in the early to mid 90's range to guarantee victory: but synthesized weapons are a must. If you defeat Solon first and quickly, you should have no problem keeping Dirna stunned as your entire party focuses their attacks on her. Solon will parry and AAA a lot, so I would suggest constant use of Fayt's "Dimension Door" Battle Skill (map it to a button so it can break guards, don't forget you can hold down the button to get more hits). It also has a chance of causing paralysis, which puts you in an even better position to take down Solon first. Keep someone with healing abilities alive and your items well stocked before the fight, and you'll be set to defeat them with ease. Once you defeat Dirna and Solon, the trophy will unlock.