With people who abuse assists, you'll want to punish that. Dante works well enough or punishing with his Million Dollars hyper. Also, one thing I found myself kicking myself for and wondering why others haven't used it at all is the cross over counter. It's a good way to get people off you if you are pressured in a corner, blocking, or they are setting up an unblockable with the help of an assist. And with a hyper right afterward, it can do some hefty damage if you set it up right.
Example: Being forced into a corner by Wolverine and an Akuma tatsu assist is coming. Cross over counter with Captain America coming in with Charging star and then cancel into Hyper charging star. From there, you can X-factor cancel, OTG, and combo both characters for an easy double kill.