Elektra is sort of like Black Widow in that she's lethal, she sleeps with who she wants, and she's more than willing to use her sexuality as a power play, so she's been sexually paired with, well, a lot of people through the years. To hear it from other characters (like Wolverine in the Enemy of the State arc), Elektra has only ever been in love once, and that was with Matt. Matt loved her, too, back in the day.
Frank labels Matt as young (in the comics Frank is 20+ years older than Matt - this is obvs changing in the MCU) naive and idealistic and an idiot sometimes, yes, and he also labels him as 'good', and something to be protected when he's not in Frank's way, but even then they both know, and admit it on the pages very often, that even though Frank threatens Matt all the time, he's not going to kill Matt, he can't do it.
Matt does go looking for Frank sometimes, he knows his heartbeat, he knows his safehouses, he knows how Frank smells, which is more of a signature to Frank and no different than the way Matt singles out anybody else by how they smell. I'd expect it to be more of a comfort than anything since Frank is a lifer dog soldier, very specific about his habits and hygiene. Maybe what's important to consider here is how often they come to blows, which is to say A LOT, over this fundamental difference, and sometimes it gets vicious and Matt does see that Frank is jailed more than once, but they always have an alliance, they know each other too well, and they rely on each other prob more than they'd like. And when they do work together, Matt makes Frank swear to not kill anyone and Frank will agree. The Omega Effect crossover, for example, where everybody was out to get DD and he let Frank watch his back? Spidey refused to let Matt be alone with Frank, he didn't trust Frank at all, but Matt trusted Frank. Peter didn't understand it, but Frank promised to not kill anyone (and used rubber bullets to protect Matt against his enemies) and didn't break his word. So you're right that it's not Frank's thing to allow evil men to survive, but (this is the big deal here) when Matt asks, he's been willing to change his fundamental beliefs for Matt. You can't see it happening the other way, though, right? Could you imagine Matt working with Frank and agreeing to kill people for as long as they're together? Me neither. :) If I HAD to, I'd say maybe the attraction is a little more one-sided from Frank's perspective, it's not like he has anybody else trying to champion the good in him, but Matt puts up with soooo much and still does soooo much for Frank and even though he thinks he's failed Frank he doesn't want to give up on him, all in spite of how much they fight and disagree, I just can't say Matt doesn't have feelings for Frank. He shouldn't, but he does. And they run deep. Whether we'll see any of that in the MCU is a good question, but I know I'd be happy just to see Matt and Frank be so different, while being so similar (once upon a time Frank was Catholic and wanted to be a priest), and fighting like they do in the comics, but becoming fast allies in spite of it all. That would be enough for me.
To get a real sense of what they mean to each other you have to read Punisher comics as well as DD comics, and you also have to read the crossovers where their relationship is scrutinised and judged by other characters. Those crossovers are the best and say a LOT about Matt and Frank, more honestly than they say about each other or themselves. There's a list of crossovers here and it's pretty good. One of the best is the Omega Effect crossover (with Spider-Man), the Confederacy of Dunces arc (DD is working with Wolverine and Spider-Man trying to catch Frank to send him to prison, but he spends half his time trying to explain Frank's code of ethics to S&W and defending Frank- it's really good), Devil By The Horns which is purely brutal but showcases Frank and Matt's ideologies very well, and the Devil In Cell Block D, if for nothing else than Frank's reaction when Matt asks him to help him break out. THAT is the closest thing I've seen to a smile on the Punisher's face in, like, ever. Frank Castle smiled for his family when they were alive, but that not-frown he gives Matt in that one moment? Holy mother of god, Matt just made the Punisher as close to truly happy as I've ever seen him over a relationship with feeeeeelings.
Re: Matt/Frank: How plausible is it really?
Frank labels Matt as young (in the comics Frank is 20+ years older than Matt - this is obvs changing in the MCU) naive and idealistic and an idiot sometimes, yes, and he also labels him as 'good', and something to be protected when he's not in Frank's way, but even then they both know, and admit it on the pages very often, that even though Frank threatens Matt all the time, he's not going to kill Matt, he can't do it.
Matt does go looking for Frank sometimes, he knows his heartbeat, he knows his safehouses, he knows how Frank smells, which is more of a signature to Frank and no different than the way Matt singles out anybody else by how they smell. I'd expect it to be more of a comfort than anything since Frank is a lifer dog soldier, very specific about his habits and hygiene. Maybe what's important to consider here is how often they come to blows, which is to say A LOT, over this fundamental difference, and sometimes it gets vicious and Matt does see that Frank is jailed more than once, but they always have an alliance, they know each other too well, and they rely on each other prob more than they'd like. And when they do work together, Matt makes Frank swear to not kill anyone and Frank will agree. The Omega Effect crossover, for example, where everybody was out to get DD and he let Frank watch his back? Spidey refused to let Matt be alone with Frank, he didn't trust Frank at all, but Matt trusted Frank. Peter didn't understand it, but Frank promised to not kill anyone (and used rubber bullets to protect Matt against his enemies) and didn't break his word. So you're right that it's not Frank's thing to allow evil men to survive, but (this is the big deal here) when Matt asks, he's been willing to change his fundamental beliefs for Matt. You can't see it happening the other way, though, right? Could you imagine Matt working with Frank and agreeing to kill people for as long as they're together? Me neither. :) If I HAD to, I'd say maybe the attraction is a little more one-sided from Frank's perspective, it's not like he has anybody else trying to champion the good in him, but Matt puts up with soooo much and still does soooo much for Frank and even though he thinks he's failed Frank he doesn't want to give up on him, all in spite of how much they fight and disagree, I just can't say Matt doesn't have feelings for Frank. He shouldn't, but he does. And they run deep. Whether we'll see any of that in the MCU is a good question, but I know I'd be happy just to see Matt and Frank be so different, while being so similar (once upon a time Frank was Catholic and wanted to be a priest), and fighting like they do in the comics, but becoming fast allies in spite of it all. That would be enough for me.
To get a real sense of what they mean to each other you have to read Punisher comics as well as DD comics, and you also have to read the crossovers where their relationship is scrutinised and judged by other characters. Those crossovers are the best and say a LOT about Matt and Frank, more honestly than they say about each other or themselves. There's a list of crossovers here and it's pretty good. One of the best is the Omega Effect crossover (with Spider-Man), the Confederacy of Dunces arc (DD is working with Wolverine and Spider-Man trying to catch Frank to send him to prison, but he spends half his time trying to explain Frank's code of ethics to S&W and defending Frank- it's really good), Devil By The Horns which is purely brutal but showcases Frank and Matt's ideologies very well, and the Devil In Cell Block D, if for nothing else than Frank's reaction when Matt asks him to help him break out. THAT is the closest thing I've seen to a smile on the Punisher's face in, like, ever. Frank Castle smiled for his family when they were alive, but that not-frown he gives Matt in that one moment? Holy mother of god, Matt just made the Punisher as close to truly happy as I've ever seen him over a relationship with feeeeeelings.