# Pastebin Z5jNaKp0
users = Array.new(3){|id|
  {
    "id"=>id,
    "username"=>"bobbyl1000",
    "scores"=>[
      {"group_id"=>nil, "percentile_score"=>"0.3669724771"},
      {"group_id"=>nil, "percentile_score"=>"0.3333333333"},
      {"group_id"=>1, "percentile_score"=>"1.0"},
      {"group_id"=>1, "percentile_score"=>"1.0"},
    ],
    "avatar"=>{
      "url"=>"https://s3.amazonaws.com/gamepredict/assets/logo-.png",
      "profile"=>{"url"=>"https://s3.amazonaws.com/gamepredict/assets/logo-profile.png"},
      "small"=>{"url"=>"https://s3.amazonaws.com/gamepredict/assets/logo-small.png"}
    }
  }
}

result = users.map{|user|
  user.merge('scores' => user['scores'].select{|h| h['group_id'] == 1 })
}

require 'pp' # for inspection
pp result