One Thousand Dead play a direct, old-school-rooted blend of thrash and death metal in the tradition of early Brazilian extreme metal. Their debut full-length Guerra, released through RTR Records in November 2022, compiles ten tracks that the band began developing during the COVID-19 pandemic after signing a multi-album deal with the label.

Onihime is a one-person brutal death/slam project based in Corrientes, Argentina, blending extreme metal with anime-themed imagery and horror. The project has released two albums, Waifu of Madness and Kult of Lamashtu, operating under the full moniker Onihime Death Cult.

Oniria is a gothic metal project from Buenos Aires active since 2005, currently operating as a solo endeavor by multi-instrumentalist and vocalist Guillermo Manolio. The band began with a fuller lineup that included guitarists, bass, and keyboards before consolidating around Manolio as the sole creative force, releasing a self-titled demo in 2005.

A one-man old school death metal project helmed by Cláudio Slayer, Open the Coffin worships the HM-2 chainsaw tone and traffics in horror imagery centered on zombies, cemetery rituals, and slasher lore. Their 2019 debut EP "Only Death Prevails" was tracked at Black Hole Studio in Natal and released through Black Hole Productions, delivering a raw, suffocating sound indebted to the Swedish death metal tradition.

Operador channel the frustrations of the Brazilian call-center grind into punishing thrash and heavy metal, with lyrics drawn directly from the monotony and dehumanization of telemarketing work. Their 2022 demo "Conexão Call Center" laid out the concept in eight tracks, and the re-recorded version released in 2023 sharpened the riffs while keeping the satirical edge intact.

Oppressus is a thrash metal band from Neiva, Huila, Colombia, formed in 2011. Their debut full-length "Humanidad in Vitro" was released in 2017, with lyrics addressing social and political nonconformity, war, death, and destruction. The band remains active as an independent act on the Colombian underground metal scene.

Opressor are an independent death metal outfit from Curitiba who have been grinding out heavy, uncompromising material since 2013. Active and unsigned, they operate squarely within the brutal death metal tradition that the Paraná underground has quietly fostered for decades.

Optofobia is a grindcore band from Merida, Venezuela. Active since at least 2014, they have released a series of EPs including "Corporotocracia" (2014), "Existencia en decadencia" (2015), and "Hacia el matadero" (2019), as well as splits with international acts like Dalle Killers and Nastiness.

Originally active between 2004 and 2009, Opus Nokturne returned in 2024 with a heavier, darker orientation, blending black and death metal textures into a progressive framework. Their debut EP "Winds of Sand," released independently in June 2025, marks the project's reintroduction with a sound that leans into dense atmospherics and compositional ambition.