So I was working on a om submission that involved lower tier pokemon, when I realised that a lot of the pokemon are just worse versions of their evolutions.
What I mean by this is there are many pokemon that perform the exact same role this is useful as it essentially doubles the strength of your win condition and allows you to play a lot more risky with each one.. Here are a few of those pairs.
+
Magnezone and magneton
Due to the fact that magneton gets a huge boost, 2 mag 2 drag can work far better than normal. The differences between these two are that magneton is faster by 20 points and is less bulky, meaning that it performs the role of a scarfer much better than magnezone, while magnezone's better bulk allows it to take a few hits form a number of steel types that don't have anything to hit steel types, and 2hko/1hko with specs. These 2 are both support roles for a team that has decided to only have these 2 pokemon to hit steel types. (if you are using them both on the same team then you may want to have one of them have hp fround and the other have hp fire.)
+
Talonflame and fletchinder
I know that many of you are of the firm belief that fletchinder is a terrible pokemon and isn't as good as talonflame in any regard. In saying this you are almost correct. There are a number of sets that talonflame is better at but there are a number of sets where the 2 are equals. Those 2 sets are sd acrobatics w/o flare blitz and spdef. However if you are using both of them on the same team then it is likely that you fill try and sweep with them, in which case fletchinder will probably be using sd acrobatics and talonflame could either use choice band or sd brave bird.
+
roserade and roselia
These two will actually have to perform two pretty different roles. The reason for this is that roserade outclasses roserlia offensively with both 10 higher speed and special attack. It also has 10 better special defense and 5 better attack. However roselia has higher hp and it can hold eviolite. All of this means that roselia will have to play a much more defensive role than roserade, which it can do while setting up hazards and healing with synthethis, and maybe even use aromatherapy, while being able to remain unpassive with giga drain and sludge bomb. roserade is still able to play a defensive role if you wish to (on the same team) but an offensive one is preffered, with acces to technician hp fire. If you have roselia with you can exchange what would normally be spikes with another offensive move like extrasensory or shadow ball or energy ball.
+
hoopa unbound and regular hoopa
If you already have hoopa unbound on your team, why not have some fun and add the other hoopa? While regular hoopa is outclassed by hoopa-u it still allows it to fill a lot of moveslots that the other one can't, due to the fact that hoopa unbound is able to use a whole host of moves. For this the 2 pokemon can pretty much run the same sets, however you should be more inclined to give hoopa-u the set that is more physically orientated.
+
Ferrothorn and ferroseed.
These two pokemon are fantastic. The two have even been used in ou by the teambuilder CTC but with ferroseed's stat boosts the pair become even better especially seems how a lot of teams struggle to deal with just one of them. The main differences between the two are that ferrothorn has higher attack and health. these two factors mean that it is much more beneficial for ferroseed to use leech seed as it gains more health and it's attacking options are worse. The two of the can share the plethora of support moves that each of them hold, with sr, spikes, thunder wave, power whip, gyro ball, leechs seed +protect and toxic it's a wonder that the pair haven't been used more.
honourable mentions
+
bisharp and pawniard
unfortunately for these two pawniard is far too weak to actually be used on a competitive team.
+
weavile and sneasel
the problem with these two is that sneasel isn't strong enough, although that isn't by much, I have used him in the past to great success when sneasel was in nu.
+
gengar+haunter
these two have almost identical stats, but their problem is that neither of them are very good, both their speed tier and special attack stat being pretty weak.