I'm a bit pissed Nedry isn't on the list as best characters. He's sure as hell the most relatable in the original film.
Dude is a very talented programmer, has staff in Cambridge so he's no jeet poser. Makes a fair bid on a job only to find out the job is way, way, way more complex than originally proposed. Forced to eat shit and keep working for his low bid or be blacklisted (in the book Hammond is way more evil about it but you see hints of it in their interactions in the film--Hammond is still the self-obsessed asshole who doesn't know when and where he needs to bend.)
Nedry clearly made the right call in assuming the park was unsustainable, its being run by an old dude that just doesn't "get it" and we can assume the espionage plans began before the death of the gatekeeper (perhaps it began when the raptors began terrorizing the feeders and they had to rapidly build the barrack solution to contain them.) Obviously Nedry was 100% right, he could see the chaos angle Malcolm also saw but Hammond refused to see. Makes sense, programming is lots of mathematics.
Nedry may seem lack empathy at first glance but he doesn't. He waits till the weekend to do his plan when the rest of the staff is on the boat awaiting to leave, limiting the chance of people being hurt when he disables the fences. We can assume that a normal weekend on the Island is just the security team, sometimes Hammond (but probably not often) and thats about it. Its a common misconception that the staff left because of the storm, that comes later. The staff was leaving as usual because it was Friday. The storm forced the boat to leave sooner than usual.
This is where Nedry's plan starts to unravel. It happens in such a way that even I as an audience member feel like I could relate. Instead of another dull weekend on the island with like 2 other dudes, the park facing closure soon due to lawsuits, the asshole owner brings in a team of civies including his own fucking grandkids. Mind you, Nedry knew damn well about the raptors being vicious killing machines and didn't fuck with their fences, only the ones he needed to disarm to get to the dock without arousing suspicion.
So these civies arrive, Nedry is locked into the plan because his cryocan has a limited cooling time and he has to get the DNA while the main staff is off the island. Damn, so relatable, haven't all of us wagies learned our works patterns and when we can slack only to have the goddamn owner surprise us once or twice?
Still, we can assume Nedry wants to succeed either to be able to get away with it or because he does have some measure of empathy and doesn't want the civies to die. Forced to run the tour he likely calculates that assuming nothing goes wrong the tour will return to the command center in time for him to execute his plan and arrive at the boat.
A few more chaotic things pile up: the storm forces the boat to leave early and one of the civies is a rule-breaking asshole and gets out of the vehicle to gawk at a dinosaur for what we can only assume was atleast 30 mins to an hour.
Really, Dr. Grant is the character that fucks everything up in JP. Had he not hoped out of his vehicle we can assume they'd have arrived back at the command center safely. In fact theres talk of cutting the tour short because of the incoming storm but sure enough Dr. Fuckitwhatever can't resist leaping into an unknown area. Hell, for all he knew he could've been wandering towards a fiberglass sick Triceratops that was used as a decoy to lure in lethal dinosaurs closer to the tracks. We know he wasn't playing around with the touchscreen map in the vehicle because he hates technology.
That detour set Nedry up for failure because he couldn't wait anylonger. Since we all know hacking isn't punching a keyboard rapidly for 30 seconds we have to assume Nedry's program was written off island and wasn't something he could tweak on a moments notice. Hence he couldn't modify the program to exclude the TRex fences.
(The only available maps of the park and tour route are only semi-canon and we must assume they aren't that detailed or even drawn to scale.) For whatever reason the tour vehicles are turned around rather than allowed to complete their loop (even though on the maps it looks like it'd be quicker to continue on--maybe Hammonds ego didn't want them seeing the other areas until they resumed the tour the next day?) Going back through the TRex paddock was especially dumb but I suspect Nedry assumed he could complete his plan before any problems occured.
Its also possible Nedry didn't expect the ride vehicles to stop while his program was running since its likely there wouldn't have been any vehicles operating as his plan was originally envisioned. We know the ride vehicles were plagued with bugs from the start of the tour.
Of course we see Nedry looking very nervous as he's forced to start his plan despite the numerous new variables he hadn't accounted for. Most of us would be nervous committing such a crime on dino island but I have a hunch that Nedry might have been nervous because he knew there were civies inside the fences he was about to shutdown. He couldn't wait any longer, in fact its possible he'd have missed the boat anyways even if he'd arrived to the port.
Nedry's one of the only employees that pushes back on Hammonds delusions, aside from Muldon (who actually suggested destroying all the Raptors so Hammond didn't even listen to his expert advice--rather building an expensive and inefficient paddock that had no safety locks nor backups for if the power went out. Hammonds ego even gets in the way of restoring power when he won't allow Malcolm to read the blueprints to Elly.
Anyways I rewatched this recently rather than watching the pile of garbage that is the newest JW movie. Nedry is as close as we get to a hero in this film while Grant is the actual immature child that fucks things up and Hammond is the delusional jerk with too much money and power.
Real shame more people can't recognize the facts. Wayne Knight is cool.
(Of course the movie was made by a covetous jew that was solicited by Universal Studios to specifically make it so they could make a ride about it--which was based more on the book--for their amusement park so we're lucky it turned out as good as it is. He also filmed it in Hawaii so he could have a nice vacation on the studios dime and also made sure the jew in the film was the "cool" guy who was always correct. Classic ego.)