Overall Miscreation deal in technically-minded death metal underpinned by themes of misanthropy, anti-religion, and apocalyptic collapse. After their 2019 debut Tales from the Abyss, they returned in 2024 with Emissary of the Great Armageddon, a seven-track record that pushes further into technical territory while keeping the songwriting rooted in blunt aggression.

Formed in Teresina around 2017, Overdose Brain play a ferocious brand of speed/thrash metal sung in Portuguese, drawing on the Brazilian underground tradition of acts like Flagelador and Cemitério. Their 2020 EP Exército Metal, recorded with vocalist Thiago Araújo, guitarist Cláudio Costa, bassist Alisson Barros, and drummer Wanderson dos Anjos, showcases cutting riffs and an uncompromising approach rooted firmly in 1990s aggression.

Overdose Nuclear coined the term "Metal do Mangue" to describe their death/thrash sound rooted in the coastal town of Ubatuba, pairing heavy riffing with socially conscious lyrics about environmental destruction and political corruption. Their 2023 album Metal do Mangue features guest appearances from Mayara Puertas of Torture Squad and Jairo Vaz Neto of Chaos Synopsis, alongside a cover of Raul Seixas's "Cowboy Fora da Lei," cementing the band's distinct identity within the Brazilian extreme metal scene.

Overlook are a Curitiba-based thrash metal outfit built around guitarist Matheus Savi, vocalist and bassist Ricardo Brito, and drummer Gabriel Cordeiro, maintaining the stripped-down aggression typical of the Brazilian underground scene. Their EP Redrum established them as a straightforward thrash act with no frills, channeling the direct energy of classic 1980s riff-driven metal.

Overnoise were a thrash metal band from Sorocaba active from 1990 through the early 2000s, featuring the sibling rhythm section of guitarist Carlos Navarro, guitarist Leandro Gamero, bassist Alex Navarro, and drummer Fernando Gamero alongside vocalist Daniel V. Filho. They released a self-titled demo in 2001 before splitting up, leaving a small but documented mark on the São Paulo state underground thrash scene.

Overthrash from Bauru trace their roots back to the late 1980s, recording demos between 1988 and 1991 before going dormant and fully reforming in 2014. Their 2016 album Until Death blends three of those original demo tracks with newly recorded material, delivering honest old-school thrash in the tradition of Slayer, Exodus, and Sepultura, with current members P.A.D. on vocals and drums, Edmir and Marcão on guitars, and Biro on bass.

Overthrow were a death metal band from Buenos Aires active from 1991 until their split-up. They contributed tracks "Devil's Eyes" and "Conquer the Fear" to the Death Metal Advance CD (1994), and released a split with Uruguayan band Morbid Blood titled Devil's Eyes / World of Violence in 1995, their side recorded at Matadero studios.

Ovvercross is a heavy metal trio built around the guitar and vocals of Bruno Oliveira, whose muscular riff-driven attack sits somewhere between classic NWOBHM and the harder-edged German heavy metal tradition. Their 2021 debut full-length Stuttgart, 1943 — preceded by the EP So Survive — is a concept record centered on the true story of a nine-year-old boy sheltering from an Allied air raid over Stuttgart, turning historical trauma into anthemic, propulsive metal.

Oxida was a short-lived speed metal outfit from Buenos Aires that emerged in 2023 and dissolved not long after, leaving behind one of the more fleeting entries in Argentina's crowded underground metal registry. The band operated squarely in the tradition of old-school speed metal — the genre Argentina helped define in the 1980s through foundational acts like V8 and early Horcas — reaching back to the era when the boundaries between NWOBHM-inspired heavy metal and the proto-thrash aggression of Motorhead-worshipping bands had yet to fully crystallize. Buenos Aires has always harbored pockets of musicians committed to this unfashionably raw style, and Oxida planted their flag firmly in that territory. Their existence was brief enough that their catalog and full lineup details remain sparse in the public record, but their registration on Encyclopaedia Metallum confirms their presence in the capital's underground scene, where speed metal never truly went out of favor. Like many underground Argentine bands of their vintage, they likely played the circuit of small venues and metal fests that form the backbone of BA's non-commercial metal ecosystem — spaces where fidelity to genre tradition matters more than trends.