One thing Doctor Who does so well is coming up with a great variety of monsters. Some turn out to be a great sucess like the Daleks and Cybermen, whilst others don't turn out so great. Since RTD took over he has brought back the Daleks, The Master, The Cybermen & The Sontarans. We have also seen the creation of a variety of new monsters like the Ood, The Hath, The Adipose e.g.
In my opinion there are 4 Villians that need briging back for series 5 & beyond; these are:
1) Rani- is a renegade Time Lord, an evil scientific genius whose villainy comes not from the usual variety of lust for power and suchlike, but from a mindset that treats everything (including morality) as secondary to her research; she has been known to enslave entire planets such as Miasimia Goria in order to have a ready supply of experimental subjects and a place to carry out her experiments uninterrupted.
2) Ice Warriors- The race originated on Mars, and first appeared in the 1967 serial The Ice Warriors where they encountered the Second Doctor and his companions Jamie and Victoria. The name Ice Warrior is not the name of their species, but was applied to them by an Earth scientific team in the Martians' first on-screen appearance.
3) Valeyyard- He is described as an aspect of the Doctor from between his twelfth and thirteenth incarnations. In the serial The Trial of a Time Lord, comprising the whole of Season 23 of the series, the Time Lords appoint the Valeyard as prosecutor at the Sixth Doctor's trial, hoping to have him executed - thereby removing the sole witness to their near-destruction of life on Earth.
4) Zygons- They first appeared in the Fourth Doctor serial Terror of the Zygons, where it was revealed that centuries ago, the Zygon homeworld was destroyed in a stellar explosion. A craft escaped and somehow made it to Earth, where it then crashed into Loch Ness. When the Doctor encountered the Zygons, they were led by a warlord named Broton. Broton wished to conquer the world to allow a refugee fleet of Zygons to colonize Earth.
What monster do you want to make a come back? Leave a comment below with your thoughts
(Information sourced from Wikepedia)