Well I wouldn't know how devastating Steven Seagal is in real life
1) Against a common thug:
This is what I am hoping to answer, and I am tending towards yes with more realistic training.
2) Against a trained fighter:
No, but Aikido wasn't intended as such and I don't see it as a failing.
In Aikido we learn to train without resistance but we must train for a common thug's resistance (at higher grades) if we are practicing Aikido also for its self defence element.
Strange...I was told multiple attackers, with bladed weapons.
"Even through surrounded by a great number of enemy
View them as one person
And so fight on!"
-from O'sensei's Doka