Destroy the Ozone layer, and let the ultraviolet radiation sterilize the Earth’s surface for you.
I’d save a few nukes for the folks huddled in caves, tho’.
With unlimited resources? Easy…
- build a time machine
- go back several billion years
- salt the Earth with your self-replicating nanobot virus
- return to the present
With this head start, your nanobots will be present EVERYWHERE on the planet, long BEFORE life begins to arise! Every living thing that even STARTS to arise will be destroyed almost immediately!
Notice that this plan takes far LESS than a week to execute!
I really didn’t want the other evil super villains to know how many resources I have on hand (they would make fun of me because I’ve kind of lagged behind), but I guess there’s now way around it. Lets say that I have unlimited money and manpower, access to hundreds of beautiful geniuses, technology that’s about 10 ahead of anything civilized man has today. I do have a time machine, but it only goes back as far as I’ve been alive (like Quantum Leap). Ahhhh, lets see what else I got looks around evil super lab. I got maybe 2 and ½ cups of anti-matter. Some kryptonite. The complete collection of Calvin and Hobbes (I’m not totally evil, I’ve got to have some outlet). A nuclear powered rocking horse. Some genetically engineered crosses of potbelly pigs and elephants (they make great pets). A space ship that can make it to Pluto and back in about 3 months (I use this mostly for joy rides). A transporter to go to the moon and back (the kind that makes a clone and destroys the original – and yes I’ve tried to keep the original, it doesn’t work that way). A plaque for “BEST EVIL EARTHLING” given to me by the sludge people of Alpha 539 (I don’t really talk to them any more, there to clingy). Some glass tubes and beakers and that’s about it.
I was thinking the exact same thing. Just in case you don’t know about Ice-9 *Aceospades, it’s a chemical that raises the freezing temperature of water to something like 68 degrees Celsius (it’s been a while since I’ve read Cat’s Craddle, so I could be off a bit). Any living being that comes in contact with it freezes instantly, and if it gets into a body of water, it will spread to all connecting bodies of water, including oceans and underground reservoirs. This will take care of all your ocean life, including bacteria and the like, but it may still leave you a few by those volcanic vaults (I have no idea how hot the temperature there gets). Also, it’s possible for life on land to survive for a while, but bring down your robot army, and you should be able to clean that off your boot in no time.
Damn, someone stole my story idea…pouts…although I was only interested in killing all the people, and didn’t care about a time limit. Of course I don’t know squat about biochemistry, so I suppose it’s my own fault for not writting it yet…sigh.
But I won’t tell you because I’m not on the moon-base list.
You’d need a huge fan and an incredibly large bottle of RoundUp. That stuff kills EVERYTHING in its path. As an added bonus, it is absorbed into the soil in 24 hours and you can start planting new stuff. 
Of course, since you didn’t pick ME to cohabitate the new and improved planet, even though I am both beautiful AND a genius, maybe I shouldn’t have given you my bright idea.
Never mind.
Build some kind of shield which completely blocks sunlight from reaching the earth. (I don’t know how long it would take for temperatures to sink to levels incompatible with life, though.)
Hmm. Take your beautiful geniuses with you as far back as you are old - what? 12, 13 years? 
- build a huge orbiting panel big enough to permanently eclipse the sun (thereby creating a devastating ice-age), along with a pretty snazzy space laser type missile defense system. Take out all the Earth’s missile launch capabilities, once you’re sure Earth can’t launch a counter attack return to the present and everything but microbes should be dead.
There may be a few scattered populations of humans living underground somehow but that’s ok. You’ll need their genetic diversity to repopulate the Earth once you dismantle the orbiting panel. Sorry kiddo, you can’t repopulate the Earth with your own seed & those beautiful geniuses despite what you’ve heard. The kids would all be too closely related.
Y’know, this is a real paradox. The mods on this board close and delete any thread that pertains to nicking music off the internet, but they ALLOW suggestions as to how to destroy the earth and its inhabitants.
Curious. 
If everyone’s dead, there’d be no one left to sue them.