Here is the full list of all 21 Battle Royale Trainer achievements.
Start any training session
Complete a round on the Urban map with the Easy AI preset
Complete a round on the Urban map with the Medium AI preset
Complete a round on the Urban map with the Hard AI preset
Complete a round on the Urban map with the Extreme AI preset
Complete a round on the Woodland map with the Easy AI preset
Complete a round on the Woodland map with the Medium AI preset
Complete a round on the Woodland map with the Hard AI preset
Complete a round on the Woodland map with the Extreme AI preset
Complete a Clear Level round on the Countryside map with the Easy AI preset
Complete a Clear Level round on the Countryside map with the Medium AI preset
Complete a Clear Level round on the Countryside map with the Hard AI preset
Complete a Clear Level round on the Countryside map with the Extreme AI preset
Complete a Battle Royale round on the Urban map with the Easy AI preset
Complete a Battle Royale round on the Urban map with the Medium AI preset
Complete a Battle Royale round on the Urban map with the Hard AI preset
Complete a Battle Royale round on the Urban map with the Extreme AI preset
Complete a Battle Royale round on the Countryside map with the Easy AI preset
Complete a Battle Royale round on the Countryside map with the Medium AI preset
Complete a Battle Royale round on the Countryside map with the Hard AI preset
Complete a Battle Royale round on the Countryside map with the Extreme AI preset