The sixteenth comic: #70 Mandrake the Magician
Mandrake the Magician is possibly the first superhero comic - it's debatable, but it's certainly a candidate. And it's a superhero in the realistic mold - although his command of hypnotism surpasses what's actually possible, and telepathy features in places, there's no super strength, no over the top displays of power, and it tries to make it all seem at least possible.
And it sort of shows. As a character, Mandrake is boring - he's the sort of boring 'perfect' man - polite, confident and universally beloved. There's just not much to it. And while other heroes sometimes started out this way too, they evolved, but Mandrake doesn't quite seem to have gotten there in the samples we've read. The sidekicks are there too. Narda is useless and unnecessary in most stories (although more useful in Doctor Congo) and Lothar starts off as a stereotype, becomes more interesting but still is the dumb, strong one.
The storylines are also a bit samey in places - crime is committed. Mandrake might be distracted or deflected (if long enough). Else he hypnotises someone or uses telepathy to get the secret out, scares them through varying means and captures them. As a clean newspaper series, it can't go any further than that.
Although stories are linked together, there's not much more continuity. I haven't spotted any recurring villains yet, for example, which could be down to my selection of stories, but doesn't lead anywhere else.