Abilities
Mordekaiser
Mordekaiser top is a really strong pick in elo lower than master. You can use your dmg to support teamfights, with ult you can fight the most fed champion in their team without any problems. The only problem is that he gets weaker the higher you climb, so dont be shocked after you lose some diamond or master matchups. You can always see my other guides for champions that are better in high elo (such as irelia).
Mordekaiser even after all this IS a strong champion to otp which you can really use to climb at least to diamond since he is quite easy and can carry games.
Matchups
Mordekaiser doesnt have A LOT of counters. His biggest counters are probably some really swift, ranged champs OR mordekaiser has a really bad matchups vs olaf and gankplank since their abilities can be used to escape Brazil :(
Summoners
Runekaiser
Important
Mordekaiser is the best on top, but you can play him mid or jungle too. He isn't that bad on these lanes and also on top I mostly ban olaf probably if I am playing mordekaiser. Mordekaiser counters champions like Illaoi, Teemo or Sett so he is a good counterpick.
Mordekaiser win conditions, laning and how strong he is 14.4
Mordekaiser Is a champion, which can splitpush and teamfight. You better play around your team since it's really hard to 1v5 if you are behind or they have a lot of cc. Mordekaiser has a strong laning phase and even stronger powerspikes (level 6 and rylai's scepter).
I would say that mordekaiser is a good but not the best toplaner in 14.4 so I would put him in A tier.