Benissimus did I great job diagnosing some of the difficulties so I'll tack my suggestions onto his. <br /><br />I'm not sure that I see a problem with using "cum" with the subjunctive as concessive (Nihil me adiuvit cum posset, C., Att., IX. 13,3), so that seems fine to me. The "is" is probably superfluous, unless one wanted to emphasize the word in which case it would more expressive to use "iste" with the force of "him, that evil man over there". <br /><br />The translation rightly (and, I think, successfully) tries to use a pair of conjunctions to link the two phrases tightly together. "Cum...autem" works well for me, though doubtless there are other pairs of conjunctions to experiment with.<br /><br />Cum malus sit, tamen non scio me putaturum esse poenam dignam esse.<br /><br />Benissimus points out well that poenae in the plural is more idiomatic and that a series of indirect statements, while not strictly ungrammatical, is to be avoided by all means. English does not have the same difficulty because each clause beginning with "that" functions like a miniature sentence, whereas in Latin the acc.+infin. structure makes it slightly more compressed.<br /><br />In order to reduce the number indirect statements I would pull out that "I think" which adds very little to the sentence except give it a slight air of non-committal. In order to reproduce this tone in Latin one could use various adverbs or, as I prefer, a parenthetical comment (which does NOT trip off indirect statement) like "opinor" or "credo". Credo tends to be more ironic and used when stating the blindingly obvious, so let us insert:<br /><br />Cum sit malus, tamen, opinor, puto poenas non esse dignas.<br /><br />(There are a handful of synonyms we could consider for puto that each suggest slightly different tones, including the verb opinari, and since it could be objected that opinor and puto are effectively repetitive one could also write: Cum sit malus, tamen opinor poenas non esse dignas -- but I like parenthetical statements)<br /><br />We might try to work the even more idiomatic phrase "dare poenas" since there good Latin prose tends to avoid abstraction in favor of vividness. We could retool the sentence:<br /><br />Cum sit malus, tamen, opinor, non fas est eum dare tantas poenas.<br /><br />With two conjunctions we are approaching well-balanced oratorical prose, perhaps if we were speaking more colloquially we might go so far as to drop out the "cum", since the subjunctive alone often conveys concession:<br /><br />Sit malus, tamen, credo, ille non meret dare poenas tantas.<br />[Note: merere, not mereri which generally takes an adverb rather than an object; also when mereo is used intransitively it means "serve as a soldier"]<br /><br />So you can see there are a lot of "correct" answers but the real difficulty and payoff of Latin is being able to choose the best-fitting sentence. This is often accomplished not by translating every word of an English sentence, but by being faithful to its spirit and intentions. Listen closely to a sentence in English: is it trying to be refined, or colloquial, humorous, or hurtful; try to determine which is the portion of the sentence that bears the most weight so that one can create a similar emphasis in the Latin. <br /><br />I hope I haven't overwhelmed you with alternatives, but shown the real subtleties which are possible in Latin! The choice of single words can have massive effects on your meaning, which is a lesson for any language.