in soulsilver i cought hoh-oh in 3ultra balls same with groudon and rayquaza. hardest was probably mewtwo in pokemon yellow. over 60 ultra ballz. oh and i cought lugia with a poke ball
dude in pokemon saffire for ds. or gameboy . its pretty hard to catch kyogre . or however u spell his name . somehow i caught him wit a water pokemon ball
the topic's question would be easier to discuss and answer if the topic was about a certain game or series of games (ex, Ruby and Saphire, Gold and Silver, Diamond and Pearl)