Niv-Mizzet, the Firemind is a famous general, which is voted as the most powerful general in color Blue and Red (another one is Jhoira of the Ghitu). There are three cards each of which can form an instant win combo with Niv (someone told me there are 4, but I have gone through many websites and can only find 3), they are Curiosity, Ophidian Eye and Mind Over Matter. For first two cards, we only need to attach either of them to Niv and tap Niv to draw a card. The triggered ability of Niv will trigger first and deal 1 damage to target opponent. Then the triggered ability of aura will trigger to let you draw a card. Niv’s triggered ability triggers again and deal 1 damage again …. This process will continue infinitely, until you kill your opponent. For Mind Over Matter, we discard a card to untap Niv and tap Niv to draw a card and deal 1 damage. Then discard again to untap Niv. Note you have drawn a card from Niv, so number of cards in your hand will not change. Thus get the infinite draw to kill other players.
Niv’s combo only require one card and there are three of them that can form the combo. Unfortunately, there is no tutor in color blue or red can tutor for enchantment, but the probability of drawing one of those three is still pretty high and there are two cards in blue has ability tranmute, which can also tutor for the enchantment. After all, it is a one card win combo when using Niv as your general.