Durant: Broken
Counters: Steelix
Strong Checks: Magneton, Qwilfish, Gligar, Poliwrath
Lesser Checks: Aggron, Sceptile, Accelgor, Entei, Scarfed Special Attackers
One Pokemon in all of RU hard counters Durant, that being Steelix, who cannot directly threaten Durant insofar as Earthquake not being an OHKO and Durant being able to switch out.
Magneton walls Durant's primary options, bar Dig, but provides free switch in opportunities to Baton Pass variants. Qwilfish should beat Durant most of the time due to the frequency of it carrying Haze/Thunder WAve/Taunt, but will lost to a CB Thunder Fang. Gligar 3HKOs Durant while being 2HKOd by Iron Head in return, Iron Head's flinch chance also benefits Durant. Poliwrath wins unless against a CB Thunder Fang.
Aggron is 2HKOd by CB Durant Iron head, Entei OHKOd by Stone Edge, the other checks cannot switch in but will revenge bar Focus Blast missing.
For offensive teams, that leaves: Aggron, Poliwrath, Entei and revenge killers as viable methods of dealing with Durant, Aggron and Poliwrath being less viable for their stealing of momentum.
Stall teams have Steelix, Qwilfish, and Gligar, although Qwilfish will be worn down without well played wish support.
Balanced teams have Magneton and the above mentioned checks and counters to check/counter Durant.
To summarize this portion, any team not running Steelix or Magneton is liable to be swept by Durant if the conditions shift slightly in Durant's favour.
So far this seems like a decent argument as to why Durant shouldn't be banned. However, should Durant achieve a Honce Claws boost, the only Pokemon that can safely switch in are Magneton and Steelix (and Poliwrath to a far lesser extent), the others being crippled, and being unable to switch in a second time.
Now, Durant, as you all know sits at an amazing speed tier, 109, which enables it to outspeed a majority of the tier without a Choice Scarf, making it very difficult to stop. Its natural power, and the threat of a Choice band will frequently cause switches, allowing for Hone Claws boosts to come unscathed. Should the attacker stay in, Durants excellent physical bulk ensures that the attack will be shrugged of easily, leaving the opponent in a worse position. If needs be it can also take weaker special attacks reasonably well.
With this said, what should be emphasized is the frequency with which Durant can set up. A large number of Durants checks and counters lack reliable recovery and, as such, cannot take Durant on multiple times. With the ease with which Durant can set up, as mentioned previously, these checks become forced to take Durant the first time, and then again when it sets up later in the match, something that is incredibly difficult to do with hazard presence and other teammates that need to be checked.
Then there is the CB Durant factor, which states that if you bring in a check to Hone Claws Durant, expecting it to set up, you get smashed by a Choice Banded move that will cripple you, case in point being Aggron. Furthermore, most teams with usually only have one solid answer to Durant, which is usually only capapble of completely stopping one variant of Durant. If the check is weakened through the course of battle, or if the Durant set is the one which the opponent cannot answer, Durant will sweep.
Hustle makes stuff miss, Hone Claws counters that, yadda yadda.
In addendum to the previous statement about the ease with which Durant can set up, it is also important to not that it is not difficult to switch it into play, due to its numerous resistances, as well as its Stealth Rock neutrality and Toxic Spikes immunity.
There's probably more to say but my mind is losing focus so i'll summarize from here.
- Only 2 Pokemon will immunize against a sweep, all other checks are beaten with small amounts of previous damage, or the correct coverage move.
- Playstyles are restricted fairly significantly in their choice of Pokemon to beat Durant.
- Huge attack stat and amazing speed makes it a deadly threat to begin with, exacerbated by Choice Band.
- Once set up with Hone Claws, very few Pokemon can take it on.
- setting up a Hone Claws is easily done due to numerous resistances, propensity to cause switches and entry hazard resistance
- Hustle boosts its power even further, accuracy drop is negated after a Hone Claws.
Additionally, Baton Pass is a very viable option on Durant. This accomplishes multiple things. Firstly, it gives Durant a means to bypass Intimidate users such as Qwilfish, boosting a second time to regain its attack boost. Secondly, it ensures that it will not lose to Magneton, passing away to survive another day. Thirdly, and most importantly, it allows Durant to pass boosts to teammates that can abuse the Honce Claws boost, for example, CB Aerodactyl, who can now spam Stone Edge's all day. This gives Durant another dimension that adds to its versatility, the elemnt of team support, where even if you manage to stop Durant it can continue the momentum and continue the threat with another dangerous sweeper.