Well, how do you define a "bad" anime in first place? Many people will instantly point at anything they personally dislike regardless of its actual quality. Being clichê for me just means the end result is a meodicre anime, not a truly terrible one so its not enough to warrant the title of "worst anime"
Ecchi, violence and other morally dubious stuff will result in wildy variated reactions depending on a multitude of factors like culture and personal background so its not a very good measure of quality either
So? What DOES qualifies a bad anime? Well, first there is animation (duh) voice acting, direction, pacing and etc.
its plain stupid to judge a anime as good or bad based on purely arbitrary personal tastes but I understand that its impossible to review something without adding your personal opinion so the ideal is examining technical quality FIRST and giving it priority over personal taste
Mars of Destruction, Chargeman Ken and Handshakers and 3 prime examples
The first two have some of the worst animation quality I ever seen in my life and the last one, despite having a actually decent one, has some nauseous, literally nauseous camera work
When even a anime can cause you motion sickness then you know its REALLY BAD.
And all 3 have some pretty garbage and nonsense plot too, its bad all across the marks