While looking imposing and intimidating, Greco is actually calm and mature when it comes to most situations, as he fights Nils fairly and square, and only watches silently towards his Gunpla's remains after losing. He's also shown to not hold grudges against opponents, evidenced by his mutual respect shared with his longtime rival, Ricardo Fellini, he also does not show any resentment or negative feelings after his defeat in the American Qualifier Finals.
Nicknamed the "Raging Bull" for his imposing apperance, Greco's fighting techniques and skills transcend this nickname. Rather than using headstrong, frontal assaults that would make full use of his Tallgeese's firepower, he puts more emphasis in delicate and precise targeting as well as the speed and superb maneuverability of his suit to achieve victory.
Greco also shows Fellini's capacity to use the terrain to his advantage, such as shooting at nearby mountains to cause debris to rain and force his opponent into the air and make them an easier target, or slowing them down with it. Even if all of his weapons have been either incapacitated or destroyed, he will still manage to weaponize the other abilities of his Gunpla and the terrain itself as well, all the while still aware of the rules.
Greco Logan was the representative fighter of America in the 6th World Tournament. He is a native of California, USA. He is the rival of Ricardo Fellini, who he fought against in the previous world tournament which came down to a sudden-death round.
Greco was able to make it to the American Qualifier Finals, having the opportunity to make it to the World Championship and therefore face his long-time rival Ricardo Fellini, who visited him a day before his fight against his opponent. While Ricardo seemed confident in Greco's abilities and strength, the American champion himself wasn't so sure; His opponent only had mere 3 months of experience at the time and was nicknamed the "Early Genius", Nils Nielsen.
On the final day of the Qualifiers, Greco stated that it would be more interesting to defeat Nils after seeing which Gunpla he'd be using. Despite making excellent use of his Tallgeese Valkyrie's abilities, he soon lost his Mega Cannon after it received a Sword-Ki attack from the Sengoku Astray. Nils offered Greco the chance to surrender and keep his Gunpla intact, but Greco's pride prevented him from giving in so easily, and asked if he was being underestimated. Greco drew out his Tallgeese's beam saber and made a brave attempt to charge against his opponent, whose Katana's easily cut through the beam lengthways and sliced off the Tallgeese's arm. Greco drew out the other saber to make another attack, but the results were virtually the same.
With Nils gradually reducing his chances to win, Greco fired up the boosters of his Tallgeese and tackled Nils's Sengoku Astray, intent on smashing the Gunpla against large boulders to score victory. Nils attempted to slow him down by burying the Katanas to the ground, but Greco triumphantly yelled out it was a useless attempt, firing up the additional boosters in his Tallgeese which effectively gave it more speed.
Just as the Sengoku Astray was about to be crushed, Nils activated a strange technique that deactivated the Tallgeese entirely, shortly before the booster pack of the Tallgeese exploded and left a flabbergasted Greco demanding what he had done. The only visible cue was the Sengoku Astray's shoulder armor covering its arms as the Tallgeese Valkyrie fell down a newly-created crater and subsequently exploded.
Although he had lost, Greco remained calm and quietly watched his destroyed Gunpla's remains.
Some time later, he gave a call to Fellini about Carlos Kaiser's defeat, surprising the Italian dandy. Greco answered that Gawain hadn't been the winner, but a young girl.
Much later during the championship, Greco attended the Gunpla Festival on the eve of the finals, accompanying fellow champions Rainer Cziommer, Luang Dallara and Fellini. He was present during Fellini's "match" against Kirara, only watching in disbelief. Later on, he was seen enjoying the festival more properly alongside Fellini.
On the last day of the championship, Greco was present to watch the fight between the team of Sei Iori and Reiji fight against PPSE's Meijin Kawaguchi, although his attentions, along with everyone else's, were centered on the sinister look that the Meijin wore, as well as the just as dark and intimidating looking Gunpla he had brought to the match. After a prolonged fight with repeated attempts from the chiefs to fix the battle towards Meijin's favor, the Star Build Strike emerged victorious and rose up to a triumphant stance. Greco stared silently as the announcer shockingly stated the World Champion, to which Greco and the crowd wildly cheered.
Their celebration was cut short, however, as the large Plavsky Crystal started resonating with Chairman Mashita's Arista, prompting it to overload the arena with smaller crystals and turn the entire stadium into a huge battlefield with a gigantic interpretation of the A Baoa Qu fortress as the center. Although Greco was incapable of participating in the massive battle against the AI Gunplas, he did assist Luang Dallara and Rainer Cziommer in evacuating the civilians to safety.
- Greco's nationality, years of experience and choice of gunpla may be a reference to the American Gundam fanbase as the franchise's popularity overseas began with Gundam Wing on Toonami, which kicked off nearly two decades before Gundam Build Fighters.