RBY Tier List
Put together an RBY tier list for OU and UU. It doesn't include all the UU, but it's a start.
OU Tier
S Rank - The big 4. These Pokémon are very difficult to counter with no significant weaknesses or if they do have weaknesses they make up for it with significant upsides and utility. They are the best and most consistent at their respective roles and they have the ability to go toe-to-toe with anything.
A Rank - These Pokémon are also extremely consistent and difficult to counter. If they have weaknesses they typically have a way to deal with their weaknesses whether by countering it or through their utility. However, these Pokémon have one small flaw or weaknesses that they can't over come. This prevents them from being S rank: Alakazam - very limited attacking move pool and low pp on psychic which can be pp stalled out. Starmie - its real weakness is Chansey with tbolt which it can't do anything to.
B Rank - These Pokémon offer significant offensive and defensive capabilities and utility. While they do have weaknesses they're strengths are able to offset those weaknesses. However, these Pokémon have one major flaw or weaknesses that they can't deal with and effectively forces them to be switched out. This prevents them from being A rank: Rhydon - can get OHKO by stab blizzard or a grass move and extremely weak to any special attack. Lapras - low speed for a special sweeper and doesn't have twave to slow the opponent down, making it extremely susceptible to electric moves. Zapdos - completely walled by ground-rock types.
C Rank - These Pokémon offer very good offensive and defensive capabilities and utility. However, they tend to have flaws and weaknesses that make them more situational and team comp dependent.
D Rank - These Pokémon are quite strong, but their flaws and weaknesses make them wildly inconsistent. They often will require the right team built around them in order to be effective.
UU Tier
Uber Rank? - These Pokémon too powerful to be played in UU, but too inconsistent to be in OU. They kind of have their own tier. Wrap Dragonite fits here.
A Rank - These Pokémon are all around consistent in UU. However, their flaws and weaknesses prevent them from being used OU, although they can sometimes be used as a surprise weapon. In UU, their weaknesses are not as major and can be overcome.
B Rank - These Pokémon offer very good offensive and defensive capabilities and utility in UU. However, they do have a few major flaws and weaknesses that make them unusable in OU, but are not as exploitable in UU. This allows them to be used in many capacities in UU.
F Rank - These Pokémon are exclusively surprise weapons and can be effective in that capacity.
Put together an RBY tier list for OU and UU. It doesn't include all the UU, but it's a start.
OU Tier
S Rank - The big 4. These Pokémon are very difficult to counter with no significant weaknesses or if they do have weaknesses they make up for it with significant upsides and utility. They are the best and most consistent at their respective roles and they have the ability to go toe-to-toe with anything.
A Rank - These Pokémon are also extremely consistent and difficult to counter. If they have weaknesses they typically have a way to deal with their weaknesses whether by countering it or through their utility. However, these Pokémon have one small flaw or weaknesses that they can't over come. This prevents them from being S rank: Alakazam - very limited attacking move pool and low pp on psychic which can be pp stalled out. Starmie - its real weakness is Chansey with tbolt which it can't do anything to.
B Rank - These Pokémon offer significant offensive and defensive capabilities and utility. While they do have weaknesses they're strengths are able to offset those weaknesses. However, these Pokémon have one major flaw or weaknesses that they can't deal with and effectively forces them to be switched out. This prevents them from being A rank: Rhydon - can get OHKO by stab blizzard or a grass move and extremely weak to any special attack. Lapras - low speed for a special sweeper and doesn't have twave to slow the opponent down, making it extremely susceptible to electric moves. Zapdos - completely walled by ground-rock types.
C Rank - These Pokémon offer very good offensive and defensive capabilities and utility. However, they tend to have flaws and weaknesses that make them more situational and team comp dependent.
D Rank - These Pokémon are quite strong, but their flaws and weaknesses make them wildly inconsistent. They often will require the right team built around them in order to be effective.
UU Tier
Uber Rank? - These Pokémon too powerful to be played in UU, but too inconsistent to be in OU. They kind of have their own tier. Wrap Dragonite fits here.
A Rank - These Pokémon are all around consistent in UU. However, their flaws and weaknesses prevent them from being used OU, although they can sometimes be used as a surprise weapon. In UU, their weaknesses are not as major and can be overcome.
B Rank - These Pokémon offer very good offensive and defensive capabilities and utility in UU. However, they do have a few major flaws and weaknesses that make them unusable in OU, but are not as exploitable in UU. This allows them to be used in many capacities in UU.
F Rank - These Pokémon are exclusively surprise weapons and can be effective in that capacity.