By complex, I assume you mean highly irregular?

I think I was being vague in my terminology. I wanted to say more broadly that German verbs are generally simpler than English ones because there are fewer tenses and aspects. There are however a greater number of strong verbs in German than in English.

I'm not familiar enough with German to evaluate. But when I think of Spanish, you've got 6 conjugations for every tense, and a whole bunch of different tenses. That makes for many dozens of different inflections, just for verbs.

English, by contrast, only has 8 regular inflections, across all parts of speech: https://en.wikipedia.org/wiki/Inflection#Examples_in_English

English does have a rich ecosystem of compound verbs (https://en.wikipedia.org/wiki/Compound_verb), but if this is taken to be part of the complexity of English verbs, I don't know how this stacks up to other languages.