Risotto figures out that Doppio must be a Stand user that the boss trusts in deeply because he’s able to hear the noise from a certain Stand. Risotto then uses his Stand Metallic against him. Metallic is able to control magnetic force and attacks Doppio. Doppio uses the part of the boss’s power he received from him. While they’re fighting, Risotto realizes that Doppio’s personality and actions seem to be changing and he realizes exactly who Doppio is.
You saw through my ability, 
and my foot got chopped off.
كشفتَ قدرتي وبُتِرَتْ قدمي
Du hast meine Fähigkeit durchschaut
und mir den Fuß abgetrennt.
Viste venir mi poder
y acabé perdiendo el pie.
Viste venir mi poder
y acabé perdiendo el pie.
J’ai vu ma jambe coupée
car tu m’as percé à jour,
Hai capito le mie mosse
e sei riuscito così a tagliarmi il piede.
Você previu minha habilidade
e me fez perder o pé.
Ты разгадал секрет моей силы 
и даже смог отрубить ногу.