arcane duelists are wizards that have become quite proficient with direct battling another caster

Designated opponent

starting at 2nd level you can use a bonus action to designate a creature within 60ft of you for one minute, that creature then becomes your designated opponent, when you cast a spell that targets your designated opponent and only your designated opponent any ability check or attack role you make with the spell is made with advantage 

you can only use this bonus action a number of times per short or long rest equal to your proficiency bonus  

Casters intuition

starting at 6th level you gain the ability to use an additional reaction so long as that reaction is used to cast a leveled spell that targets only one creature 

duelists power

starting at 10th level your designated opponent becomes more susceptible to your spells,  a designated target has disadvantage on all saving throws of your spells that target them and only them additionally if you cast a spell that deals damage that spell deals additional damage equal to your proficiency bonus 

reactive casting

starting at 14th level you gain the ability to cast spell at the casting time of a reaction, in response to your designated target making an attack role or casting a spell that you can see you can cast a spell that normally has the casting speed of one action and only targets one creature by expending a spell slot two levels higher than the level you want to cast it at