Normally, lowlifes such as yourselves would never have the opportunity to bask in such greatness. Consider yourselves fortunate.
Alfonso is known to be a coward and will do anything to keep his reputation from being tarnished as well as just to simply save his own hide. He’s also known for his arrogance and considers anyone not from the Upper City of Valua to be less than human. It is implied that he is rather stupid as well, as De Loco taunts him for pointing out the obvious and being rather slow. ("Vyse has infiltrated the mines." "Oh? What gave that away? Was it the alarms? Perhaps the sirens?") Alfonso also believes that he should be Lord Admiral and that he should not be taking orders from anyone other than the Empress herself. This is ironically achieved, as after Galcian announces his betrayal and the Armada's defection from the Valuan Monarchy, Alfonso does become Lord Admiral but never has a chance to make effective use of his new rank before dying in the Rains of Destruction.
While he is quite confident when flaunting his power, status, and wealth around, he loses all form the moment his life is threatened in any manner. Vyse's challenge at the beginning of the game was only brushed off because Alfonso underestimated him; Ramirez's and Enrique's threats to his life were far more intimidating. The fact that he would rather use personal war beasts in combat implies that he likely has no actual combat skills, a likely scenario given that very few among the Valuan upper class appreciate, let alone engage in, anything involving hard work. Alfonso's hobby is holding extravagant parties and his birthday is Silver November 6th.
Alfonso is first seen during the game’s prologue, where he is in command of an unnamed Valuan Battleship and orders the attack on Fina’s ship. Soon after securing Fina, the ship comes under attack by the Blue Rogues of the Albatross, including Vyse and Aika. Alfonso dispatches several of his Soldiers and Guards to thwart the Blue Rogues' progress, but to no avail. Alfonso quickly decides to abandon ship, but not before murdering his vice captain in order to keep him from telling anyone about his cowardly retreat. Angered by this, Vyse challenges Alfonso, who instead sends his personal war beast Antonio to deal with him and Aika and manages to escape.
This plot backfires upon Alfonso, however, as the captured battleship and its crew were released by the Air Pirates and filed a "full and accurate report" to Galcian, who relieved Alfonso of his rank as commander of the Mid Ocean fleet and confined him to Ixa'Taka indefinitely.
Later on, in their search for the Ixa’Taken priest Isapa, Vyse and crew have another encounter with Alfonso in the Valuan-controlled Moonstone Mountain. Seeking revenge for his demotion, and although in the way of De Loco's spike trap, Alfonso dispatches a second, more powerful Antonio, which is subsequently slain and lands on him upon its defeat. Alfonso later leads the attack on the Green Gigas Grendel, but Grendel punches a cruiser, causing Alfonso to panic and quickly retreat before the battle had even begun.
Alfonso is later seen with the other admirals when Galcian summons them to Dangral Island in order to announce his coup against the Empress, and to ask for their support. Amongst the admirals, Alfonso is the only voice of outright dissent, rightly accusing Galcian of high treason. However, he is too intimidated by Ramirez to do anything other than protest. After the majority of the admirals side with Galcian, Alfonso then slips away from Dangral and returns to Valua. Alfonso is quick to report the news of Galcian's betrayal to Empress Teodora I and subsequently replaces him as Lord Admiral. Alfonso did not have long to savor his new position however, as before he could assemble a counter attack, Galcian and Ramirez unleashed the Rains of Destruction from the Yellow Moon, laying waste to the Valuan Capital. Alfonso and Empress Teodora are killed by falling debris within the Imperial Palace.
Alfonso is the only admiral that players never fight at any point in the game in any way, further cementing his character as a coward.